Error "A persistence error occurred. System message follows" when trying to delete a assembly family table in Windchill PDMLink

Stack from MS log would look like:

ERROR [ajp-nio-127.0.0.1-8011-exec-8] com.ptc.core.task.Task wcadmin - Task.execute :: (wt.pom.pomResource/0) wt.pom.PersistenceException: A persistence error occurred. System message follows:
Nested exception is: wt.util.WTException: java.lang.NullPointerException
Nested exception is: java.lang.NullPointerException
(wt.pom.pomResource/0) wt.pom.PersistenceException: A persistence error occurred. System message follows:
Nested exception is: wt.util.WTException: java.lang.NullPointerException
Nested exception is: java.lang.NullPointerException
at wt.epm.workspaces.EPMTransparentWSTransactionListener.toRemove(EPMTransparentWSTransactionListener.java:99)
at wt.epm.workspaces.EPMStandardWorkspaceManager$6.notifyVetoableMultiObjectEvent(EPMStandardWorkspaceManager.java:368)
at wt.events.StandardKeyedEventBranch.intDispatchEvent(StandardKeyedEventBranch.java:306)
at wt.events.StandardKeyedEventBranch.dispatchVetoableMultiObjectEvent(StandardKeyedEventBranch.java:268)
at wt.events.StandardKeyedEventDispatcher.intDispatchEvent(StandardKeyedEventDispatcher.java:306)
at wt.events.StandardKeyedEventDispatcher.dispatchVetoableMultiObjectEvent(StandardKeyedEventDispatcher.java:244)
at wt.services.StandardManagerService.intDispatchVetoableEvent(StandardManagerService.java:412)
at wt.services.StandardManagerService.dispatchVetoableMultiObjectEvent(StandardManagerService.java:314)
at wt.vc.baseline.StandardBaselineService.dispatchVetoableMultiObjectEvent(StandardBaselineService.java:1514)
at wt.vc.baseline.StandardBaselineService.remove(StandardBaselineService.java:1017)
at wt.vc.baseline.StandardBaselineService$WTCollectionOperation.execute(StandardBaselineService.java:1498)
at wt.vc.baseline.BaselineOperation.executeTransaction(BaselineOperation.java:100)
at wt.vc.baseline.BaselineOperation.executeLockingTransaction(BaselineOperation.java:55)
at wt.vc.baseline.StandardBaselineService.removeFromBaseline(StandardBaselineService.java:704)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at wt.services.ServiceFactory$ServerInvocationHandler.invoke(ServiceFactory.java:399)
at com.sun.proxy.$Proxy358.removeFromBaseline(Unknown Source)
at wt.epm.familytable.EPMDeleteDataContainer.removeFamilyTablesToDeleteFromBaselines(EPMDeleteDataContainer.java:408)
at wt.epm.familytable.EPMStandardFamilyTableManager$FTTransactionListener.finishTransaction(EPMStandardFamilyTableManager.java:2961)
at wt.pom.TransactionManager$FinishTransactionListener.fire(TransactionManager.java:1596)
at wt.pom.TransactionManager.fireTransactionListener(TransactionManager.java:1556)
at wt.pom.TransactionManager.finishTransaction(TransactionManager.java:491)
at wt.pom.TransactionManager.commitTransaction(TransactionManager.java:439)
at wt.pom.BasicTransactionMonitor.commitTransaction(BasicTransactionMonitor.java:64)
at wt.pom.PersistentObjectManager.commitTransaction(PersistentObjectManager.java:404)
at wt.pom.Transaction.commit(Transaction.java:744)
at wt.vc.StandardVersionControlService.deleteIterations(StandardVersionControlService.java:3368)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at wt.services.ServiceFactory$ServerInvocationHandler.invoke(ServiceFactory.java:399)
at com.sun.proxy.$Proxy46.deleteIterations(Unknown Source)
at wt.dataops.delete.DeleteTask._run(DeleteTask.java:320)
at com.ptc.core.task.AtomicTask.run(AtomicTask.java:58)
at com.ptc.core.task.Task.execute(Task.java:262)
at com.ptc.core.task.StandardTaskManager.runTask(StandardTaskManager.java:183)
at com.ptc.core.task.StandardTaskManager.retryTask(StandardTaskManager.java:591)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at wt.services.ServiceFactory$ServerInvocationHandler.invoke(ServiceFactory.java:399)
at com.sun.proxy.$Proxy226.retryTask(Unknown Source)
at com.ptc.core.htmlcomp.console.RetryTaskProcessor.retryTask(RetryTaskProcessor.java:152)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at wt.htmlutil.MethodAction.action(MethodAction.java:132)
at wt.htmlutil.CachedHTMLTemplate.execute(CachedHTMLTemplate.java:162)
at wt.htmlutil.CachedHTMLTemplate.execute(CachedHTMLTemplate.java:123)
at wt.htmlutil.HTMLTemplate.process(HTMLTemplate.java:229)
at wt.templateutil.processor.DefaultTemplateProcessor.handleRequest(DefaultTemplateProcessor.java:524)
at wt.enterprise.URLProcessor.URLTemplateAction(URLProcessor.java:278)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at wt.httpgw.HTTPServletResponse.invoke(HTTPServletResponse.java:264)
at wt.httpgw.MethodRequestHandler.handleRequest(MethodRequestHandler.java:92)
at wt.httpgw.HTTPGatewayServlet.serviceWithoutFilters(HTTPGatewayServlet.java:336)
at wt.httpgw.HTTPAuthGatewayServlet.serviceWithoutFilters(HTTPAuthGatewayServlet.java:86)
at wt.httpgw.FilterChainImpl.doFilter(FilterChainImpl.java:94)
at wt.session.SessionContextDestroyer.doFilterInternal(SessionContextDestroyer.java:136)
at wt.session.SessionContextDestroyer.doFilter(SessionContextDestroyer.java:184)
at wt.httpgw.FilterChainImpl.doFilter(FilterChainImpl.java:81)
at wt.httpgw.HTTPGatewayServlet.service(HTTPGatewayServlet.java:235)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at wt.licenseusage.licensing.LicenseFilter.doFilter(LicenseFilter.java:47)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.ptc.jws.servlet.filter.WsdlServletFilter.doFilter(WsdlServletFilter.java:80)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.ptc.core.components.filter.JCAFilter.doFilter(JCAFilter.java:97)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.ptc.core.ui.validation.URLValidationFilter.doFilter(URLValidationFilter.java:86)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at wt.httpgw.filter.WTContextBeanFilter.doWithWtContextBeanHandler(WTContextBeanFilter.java:104)
at wt.httpgw.filter.WTContextBeanFilter.doFilter(WTContextBeanFilter.java:58)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at wt.servlet.CompressionFilter.doFilter(CompressionFilter.java:301)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at wt.servlet.RequestInterrupter.doFilter(RequestInterrupter.java:335)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at wt.servlet.ServletRequestMonitor.doFilter(ServletRequestMonitor.java:1660)
at wt.servlet.ServletRequestMonitorFilter.doFilter(ServletRequestMonitorFilter.java:56)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.ajp.AjpProcessor.service(AjpProcessor.java:508)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1633)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)