Fix stale state of the shortcut slot tab a11y content description

This is due to that we don't assign a none string when there's no
affordaces selected.

Test: Manually tested that it annouces none when none is selected
Bug: 280551132
Flag: None
Change-Id: Ic474c8ff6941efb4ab24aa507e9e77de360d2ba7
1 file changed