ALSA: usb-audio: Fix NULL pointer deference in try_to_register_card

ALSA: usb-audio: Fix NULL pointer deference in try_to_register_card

In try_to_register_card(), the return value of usb_ifnum_to_if() is
passed directly to usb_interface_claimed() without a NULL check, which
will lead to a NULL pointer dereference when creating an invalid
USB audio device. Fix this by adding a check to ensure the interface
pointer is valid before passing it to usb_interface_claimed().

Fixes: 39efc9c8a973 ("ALSA: usb-audio: Fix last interface check for registration")
Closes: https://lore.kernel.org/all/CANypQFYtQxHL5ghREs-BujZG413RPJGnO5TH=xjFBKpPts33tA@mail.gmail.com/
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>