ASoC: dapm: Fix NULL pointer dereference in snd_soc_dapm_free_kcontrol

w_text_param can be NULL and it is being dereferenced without checking.
Add the missing sanity check to prevent  NULL pointer dereference.
Signed-off-by: Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-dapm.c

@@ -3957,6 +3957,10 @@ snd_soc_dapm_free_kcontrol(struct snd_soc_card *card,
 	int count;
 
 	devm_kfree(card->dev, (void *)*private_value);
+
+	if (!w_param_text)
+		return;
+
 	for (count = 0 ; count < num_params; count++)
 		devm_kfree(card->dev, (void *)w_param_text[count]);
 	devm_kfree(card->dev, w_param_text);