TextInput: disable activation logic when there is a menu assigned

The edit menu has it's own logic for when to show the menu, when
to activate the input field etc upon press/release/click. So if
there is a menu, don't interfere with its logic.

Change-Id: If6af1e7b8f6bc68c66836846969cfe6bcee56de4
Reviewed-by: J-P Nurmi <jpnurmi@theqtcompany.com>