java.lang.IllegalStateException: Current thread has already started a transaction
   at org.netbeans.modules.xml.xam.AbstractModel.startTransaction(AbstractModel.java:392)
   at org.netbeans.modules.xml.xam.AbstractModel.startTransaction(AbstractModel.java:380)
   at org.netbeans.modules.maven.customizer.CustomizerProviderImpl.showCustomizer(CustomizerProviderImpl.java:170)
   at org.netbeans.modules.maven.customizer.CustomizerProviderImpl.showCustomizer(CustomizerProviderImpl.java:141)
   at org.netbeans.modules.maven.customizer.CustomizerProviderImpl.showCustomizer(CustomizerProviderImpl.java:136)
   at org.netbeans.modules.project.ui.actions.CustomizeProject.actionPerformed(CustomizeProject.java:150)
   at org.netbeans.modules.project.ui.actions.LookupSensitiveAction.actionPerformed(LookupSensitiveAction.java:170)
   at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
   at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
   at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
   at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
   at javax.swing.AbstractButton.doClick(AbstractButton.java:357)
   at javax.swing.AbstractButton.doClick(AbstractButton.java:337)
   at javax.swing.plaf.basic.BasicPopupMenuUI$BasicMenuKeyListener.menuKeyPressed(BasicPopupMenuUI.java:331)
   at javax.swing.JPopupMenu.fireMenuKeyPressed(JPopupMenu.java:1362)
   at javax.swing.JPopupMenu.processMenuKeyEvent(JPopupMenu.java:1341)
   at javax.swing.JPopupMenu.processKeyEvent(JPopupMenu.java:1325)
   at javax.swing.MenuSelectionManager.processKeyEvent(MenuSelectionManager.java:438)
   at org.netbeans.core.windows.ShortcutAndMenuKeyEventProcessor.dispatchKeyEvent(ShortcutAndMenuKeyEventProcessor.java:291)
   at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:983)
   at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:855)
   at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:676)
   at java.awt.Component.dispatchEventImpl(Component.java:4502)
   at java.awt.Container.dispatchEventImpl(Container.java:2099)
   at java.awt.Window.dispatchEventImpl(Window.java:2478)
   at java.awt.Component.dispatchEvent(Component.java:4460)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:137)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)