chat: don't crash on tab in an empty buffer
++ tab
|= pos=@ud
^- (quip card state)
- ?. =(';' (snag 0 buf.state.cli))
+ ?: ?| =(~ buf.state.cli)
+ !=(';' -.buf.state.cli)
+ ==
[~ all-state]
=+ (get-id:auto pos (tufa buf.state.cli))
=/ needle=term
