Bug 75711 AstProvider should not create AST if requested by SelectionListenerWithASTManager
3.1 M2 If SelectionListenerWithASTManager waits for an AST and the editor closes we should not create an AST for that one but return null instead.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
private Color fColor;
		
		private int fKeyModifierMask;
		
		/**
		 * The URL string if a URL was detected or <code>null</code> otherwise.
		 * @since 3.1
		 */
		private String fURLString;
		
		public void deactivate() {
			deactivate(false);
		}
		public void deactivate(boolean redrawAll) {
			if (!fActive)
				return;
			repairRepresentation(redrawAll);			
			fActive= false;
		}
		public void install() {
			ISourceViewer sourceViewer= getSourceViewer();
			if (sourceViewer == null)
				return;
				
			StyledText text= sourceViewer.getTextWidget();			
			if (text == null || text.isDisposed())
				return;
				
			updateColor(sourceViewer);