Go to Tags - Search
Press any letter, let's say "n". The system filters the tags and displays only those that have the letter "n" in it. So far so good.
Press Backspace and the system does not display the entire list of tags again.
@cool Probably a bug....
Thanks for reporting. Fixed in https://github.com/NodeBB/NodeBB/commit/9170ee831aefddc2ec4ddeff69098fb7ec6e07a4