sxmo_appmenu.sh: Never literal string grep match on empty string

scripts/core/sxmo_appmenu.sh

@@ -242,6 +242,7 @@ mainloop() {
 	cut -d'^' -f1 | 
 	dmenu -idx "$DMENUIDX" -l 14 -c -fn "Terminus-30" -p "$WINNAME" | (
 		PICKED="$(cat)"
+		echo "$PICKED" | grep . || quit
 		LOOP="$(echo "$PROGCHOICES" | grep -F "$PICKED" | cut -d '^' -f2)"
 		CMD="$(echo "$PROGCHOICES" | grep -F "$PICKED" | cut -d '^' -f3)"
 		DMENUIDX="$(echo "$PROGCHOICES" | grep -F -n "$PICKED" | cut -d ':' -f1)"