AWT events are not allowed inside write action

[Former user]

Configuration details are in the provided log file. I was able to generate PlantUML for another project without issue, but on this project (Alloy Analyzer, an open source model analyzer), it halted twice.

Unexpected exception received while running Sketch It!: java.lang.NullPointerException

Call stack: org.pmesmeur.sketchit.diagram.UmlModuleClassDiagram.getClassDiagramOutputStream(UmlModuleClassDiagram.java:37) org.pmesmeur.sketchit.diagram.UmlModuleClassDiagram.getOutputFile(UmlModuleClassDiagram.java:31) org.pmesmeur.sketchit.diagram.UmlDiagram.generate(UmlDiagram.java:32) org.pmesmeur.sketchit.diagram.UmlDiagramsGenerator.generateModuleClassDiagram(UmlDiagramsGenerator.java:44) org.pmesmeur.sketchit.diagram.UmlDiagramsGenerator.generateClassDiagrams(UmlDiagramsGenerator.java:35) org.pmesmeur.sketchit.SketchIt.generatePlantUmlDiagram(SketchIt.java:75) org.pmesmeur.sketchit.SketchIt.generatePlantUmlDiagramWithExceptionHandling(SketchIt.java:61) org.pmesmeur.sketchit.SketchIt.generatePlantUmlModel(SketchIt.java:53) org.pmesmeur.sketchit.SketchIt.actionBody(SketchIt.java:45) org.pmesmeur.sketchit.SketchIt.access$000(SketchIt.java:12) org.pmesmeur.sketchit.SketchIt$1.run(SketchIt.java:32) com.intellij.openapi.application.impl.ApplicationImpl.runWriteAction(ApplicationImpl.java:976) org.pmesmeur.sketchit.SketchIt.runInsideAnIntellijWriteAction(SketchIt.java:30) org.pmesmeur.sketchit.SketchIt.actionPerformed(SketchIt.java:24) com.intellij.openapi.actionSystem.ex.ActionUtil.performActionDumbAware(ActionUtil.java:280) com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter.lambda$actionPerformed$0(ActionMenuItem.java:296) com.intellij.openapi.wm.impl.FocusManagerImpl.runOnOwnContext(FocusManagerImpl.java:281) com.intellij.openapi.wm.impl.IdeFocusManagerImpl.runOnOwnContext(IdeFocusManagerImpl.java:77) com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter.actionPerformed(ActionMenuItem.java:285) java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967) com.intellij.openapi.actionSystem.impl.ActionMenuItem.lambda$fireActionPerformed$0(ActionMenuItem.java:112) com.intellij.openapi.application.TransactionGuardImpl.performUserActivity(TransactionGuardImpl.java:94) com.intellij.openapi.actionSystem.impl.ActionMenuItem.fireActionPerformed(ActionMenuItem.java:112) com.intellij.ui.plaf.beg.BegMenuItemUI.doClick(BegMenuItemUI.java:517) com.intellij.ui.plaf.beg.BegMenuItemUI.access$300(BegMenuItemUI.java:36) com.intellij.ui.plaf.beg.BegMenuItemUI$MyMouseInputHandler.mouseReleased(BegMenuItemUI.java:539) java.desktop/java.awt.Component.processMouseEvent(Component.java:6650) java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3345) java.desktop/java.awt.Component.processEvent(Component.java:6415) java.desktop/java.awt.Container.processEvent(Container.java:2263) java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5025) java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321) java.desktop/java.awt.Component.dispatchEvent(Component.java:4857) java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918) java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547) java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488) java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307) java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2773) java.desktop/java.awt.Component.dispatchEvent(Component.java:4857) java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:778) java.desktop/java.awt.EventQueue$4.run(EventQueue.java:727) java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721) java.base/java.security.AccessController.doPrivileged(Native Method) java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85) java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95) java.desktop/java.awt.EventQueue$5.run(EventQueue.java:751) java.desktop/java.awt.EventQueue$5.run(EventQueue.java:749) java.base/java.security.AccessController.doPrivileged(Native Method) java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85) java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:748) com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:974) com.intellij.ide.IdeEventQueue.dispatchMouseEvent(IdeEventQueue.java:912) com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:844) com.intellij.ide.IdeEventQueue.lambda$null$8(IdeEventQueue.java:449) com.intellij.openapi.progress.impl.CoreProgressManager.computePrioritized(CoreProgressManager.java:741) com.intellij.ide.IdeEventQueue.lambda$dispatchEvent$9(IdeEventQueue.java:448) com.intellij.openapi.application.impl.ApplicationImpl.runIntendedWriteActionOnCurrentThread(ApplicationImpl.java:831) com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:502) java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203) java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124) java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113) java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109) java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)