Strange delay | A function and `zle -N` for "Switch between Ripgrep launcher mode (CTRL-R) and fzf filtering mode (CTRL-F)"

- [x] I have read through the manual page (`man fzf`)
- [x] I have the latest version of fzf
- [x] I have searched through the existing issues

## Info

- OS
- [x] Linux
- [ ] Mac OS X
- [ ] Windows
- [ ] Etc.
- Shell
- [ ] bash
- [x] zsh
- [ ] fish

## My config
I've modified this line to `INITIAL_QUERY="${BUFFER:-}" ` :
https://github.com/junegunn/fzf/blob/e619b7c4f4e0da09b87a239b8f52ad909bb5f1e0/ADVANCED.md?plain=1#L423

My function and zle config:
```
# Switch between Ripgrep launcher mode (CTRL-R) and fzf filtering mode (CTRL-F)
rg-fzf-switch(){
\rm -I --preserve-root -f /tmp/rg-fzf-{r,f}
RG_PREFIX="rg --column --line-number --no-heading --color=always --smart-case "
INITIAL_QUERY="${BUFFER:-}"
FZF_DEFAULT_COMMAND="$RG_PREFIX $(printf %q "$INITIAL_QUERY")" \
fzf --query "$INITIAL_QUERY" \
--ansi \
--disabled \
--color "hl:-1:underline,hl+:-1:underline:reverse" \
--prompt 'ripgrep正则> ' \
--delimiter : \
--header '模式: CTRL-R (ripgrep) | CTRL-F (fzf)' \
--preview 'bat --color=always {1} --highlight-line {2}' \
--preview-window 'up,60%,border-bottom,+{2}+3/3,~3' \
--bind "change:reload:sleep 0.1; $RG_PREFIX {q} || true" \
--bind "ctrl-f:unbind(change,ctrl-f)+change-prompt(fzf模糊> )+enable-search+rebind(ctrl-r)+transform-query(echo {q} > /tmp/rg-fzf-r; cat /tmp/rg-fzf-f)" \
--bind "ctrl-r:unbind(ctrl-r)+change-prompt(1. ripgrep> )+disable-search+reload($RG_PREFIX {q} || true)+rebind(change,ctrl-f)+transform-query(echo {q} > /tmp/rg-fzf-f; cat /tmp/rg-fzf-r)" \
--bind "start:unbind(ctrl-r)" \
--bind "enter:become(nvr {1} +{2})"
}

zle -N rg-fzf-switch
bind '\C-F' rg-fzf-switch
```

## Problem / Steps to reproduce

The `rg` command seems to have a delay at the first time. In the second picture, there is no result. And think it's a bug or it needs some hack.


After typing `ctrl-f`:


After typing `Backspace`: