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
if ( !(element instanceof ISourceReference))
			return null;
		
		if (element.getElementType() == IJavaElement.IMPORT_DECLARATION) {
			
			IImportDeclaration declaration= (IImportDeclaration) element;
			IImportContainer container= (IImportContainer) declaration.getParent();
			ISourceRange srcRange= null;
			
			try {
				srcRange= container.getSourceRange();
			} catch (JavaModelException e) {
			}
			
			if (srcRange != null && srcRange.getOffset() == caret)
				return container;
		}
		
		return (ISourceReference) element;
	}
	/**
	 * Returns the most narrow java element including the given offset.
	 * 
	 * @param offset the offset inside of the requested element
	 * @param reconcile <code>true</code> if editor input should be reconciled in advance
	 * @return the most narrow java element
	 * @since 3.0
	 */
	protected IJavaElement getElementAt(int offset, boolean reconcile) {
		return getElementAt(offset);