Bug 30291 SearchUsagesInFileAction should show dialog in case of failures
Build I20030122 SearchUsagesInFileAction should show a dialog in failure/error cases (e.g. code resolve fails).
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/search/SearchUsagesInFileAction.java
final IWorkspaceRunnable runnable= new IWorkspaceRunnable() {
			public void run(IProgressMonitor monitor) throws CoreException {
				IJavaElement element= getInput();
				ISearchResultView view= startSearch(element.getElementName(), name);
				NameUsagesFinder finder= new NameUsagesFinder(target);
				root.accept(finder);
				List matches= finder.getUsages();
				List writeMatches= finder.getWriteUsages();
				IResource file= getResource(element);				
				for (Iterator each= matches.iterator(); each.hasNext();) {
					ASTNode node= (ASTNode) each.next();
					addMatch(
						view, 
						file, 
						createMarker(file, node, writeMatches.contains(node), 
						target instanceof IVariableBinding)
					);
				}
				searchFinished(view);
			}
		};
		run(runnable);
	}
	
	public CompilationUnit createAST() {
		IEditorInput input= fEditor.getEditorInput();
		if (input instanceof IClassFileEditorInput) {
			IClassFile classFile= ((IClassFileEditorInput)input).getClassFile();
			return AST.parseCompilationUnit(classFile, true);