Don't show context menu for member and type nodes, if they are defined in external assemblies.

src/Main/Base/Project/Dom/ClassBrowser/MemberTreeNode.cs

@@ -71,9 +71,9 @@ namespace ICSharpCode.SharpDevelop.Dom.ClassBrowser
 		
 		public override void ShowContextMenu()
 		{
-			var model = this.Model;
-			if (model is IEntityModel) {
-				var ctx = MenuService.ShowContextMenu(null, (IEntityModel) model, "/SharpDevelop/EntityContextMenu");
+			var entityModel = this.Model as IEntityModel;
+			if ((entityModel != null) && (entityModel.ParentProject != null)) {
+				var ctx = MenuService.ShowContextMenu(null, entityModel, "/SharpDevelop/EntityContextMenu");
 			}
 		}
 	}

src/Main/Base/Project/Dom/ClassBrowser/TypeDefinitionTreeNode.cs

@@ -59,9 +59,9 @@ namespace ICSharpCode.SharpDevelop.Dom.ClassBrowser
 		
 		public override void ShowContextMenu()
 		{
-			var model = this.Model;
-			if (model is IEntityModel) {
-				var ctx = MenuService.ShowContextMenu(null, (IEntityModel) model, "/SharpDevelop/EntityContextMenu");
+			var entityModel = this.Model as IEntityModel;
+			if ((entityModel != null) && (entityModel.ParentProject != null)) {
+				var ctx = MenuService.ShowContextMenu(null, entityModel, "/SharpDevelop/EntityContextMenu");
 			}
 		}
 	}