Bug 21766: Correct filtering on AUDIO_ALERT_PATH js

Bug 21766: Correct filtering on AUDIO_ALERT_PATH js

I managed to introduce a bad filter whilst backporting bug 15734 to the
18.05.x series. This patch attempts to correct that.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit f3c27b99796bd2eea82c405cfc102d0141299806)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>