prevent empty search results from being added to the result list in XamlSymbolSearch

src/AddIns/BackendBindings/XamlBinding/XamlBinding/XamlSymbolSearch.cs

@@ -107,6 +107,7 @@ namespace ICSharpCode.XamlBinding
 			if (highlighter != null) {
 				highlighter.Dispose();
 			}
+			if (results.Count > 0)
 				callback(new SearchedFile(fileName, results));
 		}
 	}