prevent null gojq results

bin/i3-focus.sh

@@ -9,6 +9,7 @@ while :; do
     case "$window" in
         'st-256color')      echo 'st'       ;;
         'Brave-browser')    echo 'Brave'    ;;
+        'null')             continue        ;;
         *)                  echo "$window"  ;;
     esac
 done