This allows to have a custom widget like the following, which would
additionally accept the line, but only in case of entries being
selected:
fzf-file-widget-with-accept() {
zle fzf-file-widget
if [[ "$?" == 0 ]] && (( $#BUFFER )); then
zle accept-line
fi
}
zle -N fzf-file-widget-with-accept
bindkey '\e^T' fzf-file-widget-with-accept
With this `<C-a>t` will launch fzf, and simulate the pressing of "Enter"
afterwards.