fix possible NullReferenceExceptions in ResolveExtensionMethod; shoul…

…d fix http://usagedatacollector.sharpdevelop.net/analysis/ExceptionGroup/Edit/229

src/AddIns/Misc/SharpRefactoring/Project/Src/MenuItemFactories/ResolveExtensionMethod.cs

@@ -28,21 +28,24 @@ public MenuItem Create(RefactoringMenuContext context)
 				return null;
 			if (!(context.ResolveResult is UnknownMethodResolveResult))
 				return null;
+			if (context.ProjectContent == null)
+				return null;
 
 			UnknownMethodResolveResult rr = context.ResolveResult as UnknownMethodResolveResult;
 
+			if (rr.CallingClass == null)
+				return null;
+
 			MenuItem item = new MenuItem() {
 				Header = string.Format(StringParser.Parse("${res:AddIns.SharpRefactoring.ResolveExtensionMethod}"), rr.CallName),
 				Icon = ClassBrowserIconService.GotoArrow.CreateImage()
 			};
 
 			List<IClass> results = new List<IClass>();
 
-			IProjectContent pc = rr.CallingClass.ProjectContent;
-
-			SearchAllExtensionMethodsWithName(results, pc, rr.CallName);
+			SearchAllExtensionMethodsWithName(results, context.ProjectContent, rr.CallName);
 
-			foreach (IProjectContent content in pc.ReferencedContents)
+			foreach (IProjectContent content in context.ProjectContent.ReferencedContents)
 				SearchAllExtensionMethodsWithName(results, content, rr.CallName);
 
 			if (!results.Any())