Fix recently introduced bug when opening files with other than C#/VB content.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@6188 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/Main/Base/Project/Src/Services/RefactoringService/ContextActions/EditorASTProvider.cs

@@ -84,7 +84,14 @@ namespace ICSharpCode.SharpDevelop.Refactoring
 		{
 			if (editor == null || editor.Language == null)
 				return null;
-			return new NRefactoryResolver(editor.Language.Properties);
+			try
+			{
+				return new NRefactoryResolver(editor.Language.Properties);
+			}
+			catch(NotSupportedException)
+			{
+				return null;
+			}
 		}
 		
 		SupportedLanguage? GetEditorLanguage(ITextEditor editor)