Fixed unhandled InvalidCastException when using the keyboard with a Form being displayed in the designer.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@5080 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/AddIns/DisplayBindings/FormsDesigner/Project/Src/FormKeyHandler.cs

@@ -76,8 +76,9 @@ namespace ICSharpCode.FormsDesigner
 			if (formDesigner == null || formDesigner.Host == null) {
 				return false;
 			}
-			if (!((Control)formDesigner.Control).ContainsFocus)
+			if (formDesigner.UserContent != null && !((Control)formDesigner.UserContent).ContainsFocus) {
 				return false;
+			}
 			
 			Control originControl = Control.FromChildHandle(m.HWnd);
 			if (originControl != null && formDesigner.UserContent != null && !(formDesigner.UserContent == originControl || formDesigner.UserContent.Contains(originControl))) {