Fix trying to play sound on null audio object
Fix trying to play sound on null audio object

Stopping the waiting sound nullifies the "backgroundAudio" object used
to play that sound, so the interval handler needs to be aborted after
stopping it.

Signed-off-by: Daniel Calviño Sánchez <bd7629e975cc0e00ea7cda4ab6a120f2ee42ac1b@gmail.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed