Unable to open .java files

[wihtiko]

Trying to open any java code file results in this error:

java.lang.NullPointerException
at org.netbeans.modules.editor.fold.ui.CodeFoldingSideBar.resolveBackColor(CodeFoldingSideBar.java:353)
at org.netbeans.modules.editor.fold.ui.CodeFoldingSideBar.updateColors(CodeFoldingSideBar.java:368)
at org.netbeans.modules.editor.fold.ui.CodeFoldingSideBar.access$200(CodeFoldingSideBar.java:99)
at org.netbeans.modules.editor.fold.ui.CodeFoldingSideBar$2.preferenceChange(CodeFoldingSideBar.java:231)
at org.netbeans.modules.editor.fold.ui.CodeFoldingSideBar.addNotify(CodeFoldingSideBar.java:287)
at java.desktop/java.awt.Container.addNotify(Container.java:2800)
at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4783)
at org.netbeans.modules.editor.impl.CustomizableSideBar$WestSidebarHolder.addNotify(CustomizableSideBar.java:286)
at java.desktop/java.awt.Container.addNotify(Container.java:2800)
at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4783)
at java.desktop/java.awt.Container.addNotify(Container.java:2800)
at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4783)
at java.desktop/java.awt.Container.addNotify(Container.java:2800)
at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4783)
at java.desktop/java.awt.Container.addImpl(Container.java:1146)
at java.desktop/java.awt.Container.add(Container.java:997)
at org.openide.text.CloneableEditorInitializer.initCustomEditor(CloneableEditorInitializer.java:523)
at org.openide.text.CloneableEditorInitializer.initCustomEditorAndDecorationsInEDT(CloneableEditorInitializer.java:573)
[catch] at org.openide.text.CloneableEditorInitializer.run(CloneableEditorInitializer.java:321)
at org.openide.text.CloneableEditorInitializer.processPendingEDTRequests(CloneableEditorInitializer.java:135)
at org.openide.text.CloneableEditorInitializer$1.run(CloneableEditorInitializer.java:84)
at org.netbeans.core.windows.WindowManagerImpl$Exclusive$1.run(WindowManagerImpl.java:1615)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:136)
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)

Windows 10. Reinstall did not help.