Fix Typo

Forgot quotes in if statement.

mpris_firefox_playstatus.sh

@@ -2,7 +2,7 @@
 
 firefox_mpris_dbus=$(dbus-send --print-reply --dest=org.freedesktop.DBus  /org/freedesktop/DBus org.freedesktop.DBus.ListNames | grep -Po "org.mpris.*firefox[^\"]+")
 
-if [ -n $firefox_mpris_dbus ]; then
+if [ -n "${firefox_mpris_dbus}" ]; then
   playback_string=$(dbus-send --print-reply --dest=${firefox_mpris_dbus} /org/mpris/MediaPlayer2 org.freedesktop.DBus.Properties.Get string:'org.mpris.MediaPlayer2.Player' string:'PlaybackStatus' | grep -Po "(?<=string \")[^\"]+")
 
   echo "Firefox MPRIS Instance ${firefox_mpris_dbus} has playback status ${playback_string}"