Fix seagl-setup-app crashing with no args

bin/seagl-setup-app

@@ -3,6 +3,10 @@
 set -euo pipefail
 set -x
 
+# XXX this doesn't work if the user actually *explicitly* passes empty string, i.e.
+# seagl-setup-app ''
+arg="${1-empty string}"
+
 if [ $(id -u) == 0 ]; then
 	echo fatal: cannot be run as root >&2
 	exit 1
@@ -19,15 +23,15 @@ function start_and_link_app() {
 	nohup gio launch $desktop_file_full >/dev/null 2>&1
 }
 
-if [ $1 == obs ]; then
+if [ "$arg" == obs ]; then
 	# TODO provision RTMP keys
 	start_and_link_app com.obsproject.Studio
-elif [ $1 == nextcloud ]; then
+elif [ "$arg" == nextcloud ]; then
 	nextcloud --userid 2024laptops --apppassword "$(jq .nextcloudAppPassword < /var/lib/seagl/config-data.json)" --isvfsenabled 0 --serverurl 'https://cloud.seagl.org/'
 	start_and_link_app com.nextcloud.desktopclient.nextcloud
-elif [ $1 == firefox ]; then
+elif [ "$arg" == firefox ]; then
 	sudo sed -i "s;AV_TEST_RESULTS_PLACEHOLDER;$(jq .avTestResultsSheetURL < /var/lib/seagl/config-data.json);" /etc/firefox/policies/policies.json
 	start_and_link_app org.mozilla.firefox
 else
-	echo fatal: application to be set up must be one of obs, nextcloud, firefox
+	echo fatal: application to be set up must be one of obs, nextcloud, firefox, but received $arg
 fi