work around bugs in kitty where it hangs on close

All terminals quit when the child process terminates. Except
kitty. Kitty doesn't quit until there are no open file
descriptors to the tty.

And the best thing? This is "better". Having the balls to
claim this nasty bug as feature is worthy of admiration.

internal/worker.zsh

@@ -181,6 +181,7 @@ function _p9k_worker_start() {
     _p9k__worker_file_prefix=${TMPDIR:-/tmp}/p10k.worker.$EUID.$sysparams[pid].$EPOCHSECONDS
 
     sysopen -r -o cloexec -u _p9k__worker_resp_fd <(
+      exec 0</dev/null
       if [[ -n $_POWERLEVEL9K_WORKER_LOG_LEVEL ]]; then
         exec 2>$_p9k__worker_file_prefix.log
         setopt xtrace