zsh:conf: Fix HOME fallback

Actually use `_get_config_dir`'s exit code instead of `local`'s (i.e.
always™ zero). This was broken since always.

.config/zsh/zshrc.d/40-functions.zsh

@@ -95,8 +95,8 @@ conf() {
 	1="${(*)1%%/#}"
 
 	# search for program name in XDG_CONFIG_HOME and $HOME
-	local CONF_DIR="$(_get_config_dir "$1")"
+	local CONF_DIR
-	if (( $? )); then
+	if ! CONF_DIR="$(_get_config_dir "$1")"; then
 		printf "\033[1;31mFalling back to $HOME.\n\033[0m" >&2
 		CONF_DIR="$HOME"
 	fi