Show action error for device assistant action when no assistant is installed

[jambl3r]

You can choose the 'open device assistant' action but when you press test it says 'device has no assistant'.

[sds100]

The user can still select it because it could potentially work, so it should show an error like other actions.

[jambl3r]

It shows a toast message already, is that what you mean?

[sds100]

The action should be highlighted red that something is wrong, like when the key code action needs the input method turned on