StatusChatListCategory menu button breaks when no popup menu is provided

[0x-r4bbit]

This is something that came up while building #133

Even though, this might not necessarily happen in practice, when a StatusChatListCategory is used and doesn't have a popupMenu for it's menuButton, the underlying StatusChatListCategoryItem breaks the menu button's state and also throws and error, because it tries to open a popup menu regardless.

The solution here is to either return early in the menu button trigger when there's no popup menu, or allow to individually hide the menu button (notice that the add button isn't affected by this), similar to #152