ALSA - hda: hdmi check NULL pointer in hdmi_set_chmap

Make sure per_pin is not NULL before using it.

Fixes: 9b3dc8aa3f ('ALSA: hda - Register chmap obj as priv data instead of codec')
Signed-off-by: Libin Yang <libin.yang@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_hdmi.c

@@ -1858,6 +1858,8 @@ static void hdmi_set_chmap(struct hdac_device *hdac, int pcm_idx,
 	struct hdmi_spec *spec = codec->spec;
 	struct hdmi_spec_per_pin *per_pin = pcm_idx_to_pin(spec, pcm_idx);
 
+	if (!per_pin)
+		return;
 	mutex_lock(&per_pin->lock);
 	per_pin->chmap_set = true;
 	memcpy(per_pin->chmap, chmap, ARRAY_SIZE(per_pin->chmap));