[BUG] tmux-popup sometimes cause extra characters

[Aloxaf]

Describe the bug

If a user types something before tmux popup shows, these characters will be print directly to the commandline, not taken as the input of fzf.

To Reproduce Steps to reproduce the behavior:

1. Run _tst() { sleep 2; compadd d c b a }; compdef _tst tst
2. Type 'tst '
3. Press Tab and type 'abc' immediately.

Expected behavior 'abc' is taken as the input of fzf