ALSA: usb-audio: WARN_ON when alts is passed as NULL
ALSA: usb-audio: WARN_ON when alts is passed as NULL

Prevent NULL dereference in snd_usb_add_endpoints(), when
alts is passed as NULL. In this case, WARN (since this is
a non-fatal bug) and return NULL ep. Call sites treat a NULL
return value as an error.

Signed-off-by: Eldad Zack <46870ccd9486ced5844a21b823ddb0e89874ecb6@fogrefinery.com>
Signed-off-by: Takashi Iwai <4596b3305151c7ee743192a95d394341e3d3b644@suse.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs