ALSA: usb-audio: Always initialize fixed_rate in snd_usb_find_implicit_fb_sync_format()

Handle the fallback code path, too.

Fixes: fd28941c ("ALSA: usb-audio: Add new quirk FIXED_RATE for JBL Quantum810 Wireless")
BugLink: https://lore.kernel.org/alsa-devel/Y7frf3N%2FxzvESEsN@kili/Reported-by: Dan Carpenter <error27@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230109141133.335543-1-perex@perex.czSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/implicit.c

@@ -471,7 +471,7 @@ snd_usb_find_implicit_fb_sync_format(struct snd_usb_audio *chip,
 	subs = find_matching_substream(chip, stream, target->sync_ep,
 				       target->fmt_type);
 	if (!subs)
-		return sync_fmt;
+		goto end;
 
 	high_score = 0;
 	list_for_each_entry(fp, &subs->fmt_list, list) {
@@ -485,6 +485,7 @@ snd_usb_find_implicit_fb_sync_format(struct snd_usb_audio *chip,
 		}
 	}
 
+ end:
 	if (fixed_rate)
 		*fixed_rate = snd_usb_pcm_has_fixed_rate(subs);
 	return sync_fmt;

sound/usb/pcm.c

@@ -163,6 +163,8 @@ bool snd_usb_pcm_has_fixed_rate(struct snd_usb_substream *subs)
 	struct snd_usb_audio *chip = subs->stream->chip;
 	int rate = -1;
 
+	if (!subs)
+		return false;
 	if (!(chip->quirk_flags & QUIRK_FLAG_FIXED_RATE))
 		return false;
 	list_for_each_entry(fp, &subs->fmt_list, list) {