ASoC: core: Check for rtd == NULL in snd_soc_remove_pcm_runtime()

snd_soc_remove_pcm_runtime() might be called with rtd == NULL which will
leads to null pointer dereference.
This was reproduced with topology loading and marking a link as ignore
due to missing hardware component on the system.
On module removal the soc_tplg_remove_link() would call
snd_soc_remove_pcm_runtime() with rtd == NULL since the link was ignored,
no runtime was created.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

Author: ujfalusi

sound/soc/soc-core.c

@@ -1139,6 +1139,9 @@ static int snd_soc_compensate_channel_connection_map(struct snd_soc_card *card,
 void snd_soc_remove_pcm_runtime(struct snd_soc_card *card,
 				struct snd_soc_pcm_runtime *rtd)
 {
+	if (!rtd)
+		return;
+
 	lockdep_assert_held(&client_mutex);
 
 	/*