The skins2 code checked for the audio volume to be zero. However the audio is muted with by caling
the function aout_SetMute() or aout_ToggleMute(). Use aout_IsMuted() to test for muted audio.
(cherry picked from commit 4f96ae4a9bf70543b421e1b039cad0356a696b92)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>