Failure to refresh the highlighted gizmo meant that clicking
on a highlighted gizmo would attempt to activate it even though
it's poll function failed - which crashed in this case.
Resolve the common-case by ensuring a call to refresh the gizmo-map
causes the event system to re-evaluate the highlighted gizmo,
even if the cursor doesn't move.
Since it's still possible the call to "refresh" the gizmo is missed,
gizmo_tweak_invoke now checks the gizmo-groups poll succeeds with an
assert and early return if it doesn't. This would have prevented the
crash although the highlighted-gizmo still won't be reset - causing
the cursor to display as if it's over a gizmo until it's moved.
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