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/ASTProvider.java
}
	/**
	 * Returns a shared compilation unit AST for the given
	 * Java element.
	 * <p>
	 * Clients are not allowed to modify the AST and must
	 * synchronize all access to its nodes.
	 * </p>
	 * 
	 * @param je				the Java element
	 * @param wait				<code>true</code> if the client wants to wait for the result,
	 * 								<code>null</code> will be returned if the AST is not ready and
	 * 								the client does not want to wait
	 * @param progressMonitor	the progress monitor
	 * @return					the AST or <code>null</code> if the AST is not available
	 */
	public CompilationUnit getAST(IJavaElement je, boolean wait, IProgressMonitor progressMonitor) {
		Assert.isTrue(je != null && (je.getElementType() == IJavaElement.CLASS_FILE || je.getElementType() == IJavaElement.COMPILATION_UNIT));
		
		if (progressMonitor != null && progressMonitor.isCanceled())
			return null;
		
		synchronized (this) {
			if (je.equals(fActiveJavaElement)) {
				if (fAST != null || !wait)
					return fAST;
			}
		}
		if (isReconciling(je)) {
			try {