Allow Targeting with Hidden UI

[AstralWanderer]

The UI in TOME can be hidden using Alt-W which is handy for situations where enemies are hidden under toolbars. However it currently isn't possible to target anything with a talent when the UI is hidden except via the right-click menu (which itself gets unwieldy very quickly).

It would be handy if a talent could be selected (with UI visible), the UI then hidden, but with the target selector remaining active (rather than being disabled).