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
sourceViewer.addTextInputListener(this);
			
			IDocument document= sourceViewer.getDocument();
			if (document != null)
				document.addDocumentListener(this);			
			text.addKeyListener(this);
			text.addMouseListener(this);
			text.addMouseMoveListener(this);
			text.addFocusListener(this);
			text.addPaintListener(this);
			
			((ITextViewerExtension4)sourceViewer).addTextPresentationListener(this);
			
			updateKeyModifierMask();
			
			IPreferenceStore preferenceStore= getPreferenceStore();
			preferenceStore.addPropertyChangeListener(this);
		}
		
		private void updateKeyModifierMask() {
			String modifiers= getPreferenceStore().getString(BROWSER_LIKE_LINKS_KEY_MODIFIER);
			fKeyModifierMask= computeStateMask(modifiers);
			if (fKeyModifierMask == -1) {
				
				fKeyModifierMask= getPreferenceStore().getInt(BROWSER_LIKE_LINKS_KEY_MODIFIER_MASK);
			}
		}
		private int computeStateMask(String modifiers) {
			if (modifiers == null)
				return -1;