Bug #25583,27681,24193 when unloading the 3-pane window, close the msg window

r=sspitzer

mailnews/base/resources/content/msgMail3PaneWindow.js

@@ -286,6 +286,8 @@ function OnUnloadMessenger()
 			messenger.SetWindow(null, null);
 		}
 	}
+
+  msgWindow.closeWindow();
 }