Minor Description
There are some preconditions to this exception that I can't reproduce anymore. I was playing with regex for DB Import table name match, and the Modeler was misbehaving somehow (wouldn't let me enter certain forms of regex, etc). Then I deleted that probelmatic include and tried to add a new one. That's when the exception happened.
CayenneModeler Info Version: 4.2.M1 Build Date: Apr 07 2020 08:40:10 Exception: ================================= java.lang.NullPointerException at org.apache.cayenne.modeler.action.dbimport.TreeManipulationAction.canBeInserted(TreeManipulationAction.java:157) at org.apache.cayenne.modeler.action.dbimport.AddIncludeTableAction.performAction(AddIncludeTableAction.java:54) at org.apache.cayenne.modeler.util.CayenneAction.actionPerformed(CayenneAction.java:171) at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967) at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308) at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405) at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262) at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279) at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:297) at java.desktop/java.awt.Component.processMouseEvent(Component.java:6632) at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342) at java.desktop/java.awt.Component.processEvent(Component.java:6397) at java.desktop/java.awt.Container.processEvent(Container.java:2263) at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5008) at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321) at java.desktop/java.awt.Component.dispatchEvent(Component.java:4840) at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918) at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547) at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488) at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307) at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2762) at java.desktop/java.awt.Component.dispatchEvent(Component.java:4840) at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772) at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721) at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715) at java.base/java.security.AccessController.doPrivileged(AccessController.java:389) at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85) at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95) at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745) at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743) at java.base/java.security.AccessController.doPrivileged(AccessController.java:389) at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85) at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742) at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203) at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124) at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113) at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109) at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)