[native] Display user list only when tag input is empty or text input is not empty
[native] Display user list only when tag input is empty or text input is not empty

Test Plan:
Open thread search - user list should be visible. Select an user - user list should disappear. Search for another user - the list should appear.
Additionally, when a list is not visible, the separator should not be displayed.

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: KatPo, zrebcu411, Adrian

Differential Revision: https://phabricator.ashoat.com/D546

Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal,Ashoat/squadcal