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How to fix this error? java.lang.NullPointerException: Cannot invoke "javax.swing.text.AttributeSet.getAttribute(Object)" because "attr" is null 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$2.preferenceChange(CodeFoldingSideBar.java:231) at org.netbeans.modules.editor.fold.ui.CodeFoldingSideBar.addNotify(CodeFoldingSideBar.java:287) at java.desktop/java.awt.Container.addNotify(Container.java:2804) at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4846) at org.netbeans.modules.editor.impl.CustomizableSideBar$WestSidebarHolder.addNotify(CustomizableSideBar.java:288) at...