PsiViewer exception

After switching IDEA JDK for a project:
-

Argument 1 for @NotNull parameter of com/intellij/psi/util/PsiTreeUtil.isAncestor
must not be null
java.lang.IllegalArgumentException: Argument 1 for @NotNull parameter of
com/intellij/psi/util/PsiTreeUtil.isAncestor must not be null
at com.intellij.psi.util.PsiTreeUtil.isAncestor(PsiTreeUtil.java)
at idea.plugin.psiviewer.controller.project.EditorListener.isElementChangedUnderViewerRoot(EditorListener.java:106)
at idea.plugin.psiviewer.controller.project.EditorListener.updateTreeFromPsiTreeChange(EditorListener.java:96)
at idea.plugin.psiviewer.controller.project.EditorListener.access$000(EditorListener.java:46)
at idea.plugin.psiviewer.controller.project.EditorListener$1.propertyChanged(EditorListener.java:89)
at com.intellij.psi.impl.PsiManagerImpl.a(PsiManagerImpl.java:527)
at com.intellij.psi.impl.PsiManagerImpl.propertyChanged(PsiManagerImpl.java:71)
at com.intellij.psi.impl.file.impl.FileManagerImpl$MyModuleRootListener$2.run(FileManagerImpl.java:8)
at com.intellij.openapi.application.impl.ApplicationImpl.runWriteAction(ApplicationImpl.java:270)
at com.intellij.psi.impl.file.impl.FileManagerImpl$MyModuleRootListener.rootsChanged(FileManagerImpl.java:16)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.intellij.util.messages.impl.MessageBusConnectionImpl.deliverMessage(MessageBusConnectionImpl.java:85)
at com.intellij.util.messages.impl.MessageBusImpl.pumpMessages(MessageBusImpl.java:144)
at com.intellij.util.messages.impl.MessageBusImpl.sendMessage(MessageBusImpl.java:136)
at com.intellij.util.messages.impl.MessageBusImpl.access$000(MessageBusImpl.java:19)
at com.intellij.util.messages.impl.MessageBusImpl$2.invoke(MessageBusImpl.java:84)
at $Proxy65.rootsChanged(Unknown Source)
at com.intellij.openapi.roots.impl.ProjectRootManagerImpl.rootsChanged(ProjectRootManagerImpl.java:137)
at com.intellij.openapi.roots.impl.ProjectRootManagerImpl.a(ProjectRootManagerImpl.java:142)
at com.intellij.openapi.roots.impl.ProjectRootManagerImpl.setProjectJdk(ProjectRootManagerImpl.java:354)
at com.intellij.openapi.roots.ui.configuration.ProjectJdkConfigurable.apply(ProjectJdkConfigurable.java:54)
at com.intellij.openapi.roots.ui.configuration.ProjectConfigurable$3.run(ProjectConfigurable.java:13)
at com.intellij.openapi.application.impl.ApplicationImpl.runWriteAction(ApplicationImpl.java:270)
at com.intellij.openapi.roots.ui.configuration.ProjectConfigurable.apply(ProjectConfigurable.java:10)
at com.intellij.openapi.roots.ui.configuration.projectRoot.ProjectRootConfigurable.apply(ProjectRootConfigurable.java:146)
at com.intellij.ide.ui.search.DefaultSearchableConfigurable.apply(DefaultSearchableConfigurable.java:9)
at com.intellij.openapi.options.ex.SingleConfigurableEditor$ApplyAction.actionPerformed(SingleConfigurableEditor.java:6)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.java:5501)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3135)
at java.awt.Component.processEvent(Component.java:5266)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3968)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Window.dispatchEventImpl(Window.java:1778)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at com.intellij.ide.IdeEventQueue.b(IdeEventQueue.java:131)
at com.intellij.ide.IdeEventQueue.a(IdeEventQueue.java:7)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:153)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:153)
at java.awt.Dialog$1.run(Dialog.java:525)
at java.awt.Dialog$2.run(Dialog.java:553)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Dialog.java:551)
at com.intellij.openapi.ui.impl.DialogWrapperPeerImpl$MyDialog.show(DialogWrapperPeerImpl.java:81)
at com.intellij.openapi.ui.impl.DialogWrapperPeerImpl.show(DialogWrapperPeerImpl.java:127)
at com.intellij.openapi.ui.DialogWrapper.show(DialogWrapper.java:748)
at com.intellij.openapi.options.ex.ControlPanelSettingsEditor.b(ControlPanelSettingsEditor.java:5)
at com.intellij.openapi.options.ex.ControlPanelSettingsEditor.access$300(ControlPanelSettingsEditor.java:80)
at com.intellij.openapi.options.ex.ControlPanelSettingsEditor$MyKeyAdapter.keyReleased(ControlPanelSettingsEditor.java:43)
at java.awt.Component.processKeyEvent(Component.java:5462)
at javax.swing.JComponent.processKeyEvent(JComponent.java:2722)
at java.awt.Component.processEvent(Component.java:5278)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3968)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1826)
at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:677)
at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:934)
at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:806)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:641)
at java.awt.Component.dispatchEventImpl(Component.java:3841)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Window.dispatchEventImpl(Window.java:1778)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at com.intellij.ide.IdeEventQueue.b(IdeEventQueue.java:131)
at com.intellij.ide.IdeEventQueue.a(IdeEventQueue.java:29)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:153)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:153)
at java.awt.Dialog$1.run(Dialog.java:525)
at java.awt.Dialog$2.run(Dialog.java:553)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Dialog.java:551)
at com.intellij.openapi.ui.impl.DialogWrapperPeerImpl$MyDialog.show(DialogWrapperPeerImpl.java:81)
at com.intellij.openapi.ui.impl.DialogWrapperPeerImpl.show(DialogWrapperPeerImpl.java:127)
at com.intellij.openapi.ui.DialogWrapper.show(DialogWrapper.java:748)
at com.intellij.ide.actions.ShowSettingsUtilImpl.showControlPanelOptions(ShowSettingsUtilImpl.java:38)
at com.intellij.ide.actions.ShowSettingsUtilImpl.showSettingsDialog(ShowSettingsUtilImpl.java:24)
at com.intellij.ide.actions.ShowSettingsAction.actionPerformed(ShowSettingsAction.java:3)
at com.intellij.openapi.keymap.impl.IdeKeyEventDispatcher.a(IdeKeyEventDispatcher.java:151)
at com.intellij.openapi.keymap.impl.IdeKeyEventDispatcher.b(IdeKeyEventDispatcher.java:111)
at com.intellij.openapi.keymap.impl.IdeKeyEventDispatcher.dispatchKeyEvent(IdeKeyEventDispatcher.java:10)
at com.intellij.ide.IdeEventQueue.a(IdeEventQueue.java:144)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:153)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)