ASoC: Intel: Skylake: Fix potential null pointer dereference

Check if the next sink is not null to avoid potential null pointer
dereference in skl_tplg_bind_sinks().

Signed-off-by: Guneshwor Singh <guneshwor.o.singh@intel.com>
Acked-By: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/skylake/skl-topology.c

@@ -925,7 +925,7 @@ static int skl_tplg_bind_sinks(struct snd_soc_dapm_widget *w,
 		}
 	}
 
-	if (!sink)
+	if (!sink && next_sink)
 		return skl_tplg_bind_sinks(next_sink, skl, src_w, src_mconfig);
 
 	return 0;