ASoC: SOF: avoid a NULL dereference with unsupported widgets

If an IPC4 topology contains an unsupported widget, its .module_info
field won't be set, then sof_ipc4_route_setup() will cause a kernel
Oops trying to dereference it. Add a check for such cases.

Cc: stable@vger.kernel.org # 6.2
Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20230329113828.28562-1-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ipc4-topology.c

@@ -1805,6 +1805,14 @@ static int sof_ipc4_route_setup(struct snd_sof_dev *sdev, struct snd_sof_route *
 	u32 header, extension;
 	int ret;
 
+	if (!src_fw_module || !sink_fw_module) {
+		/* The NULL module will print as "(efault)" */
+		dev_err(sdev->dev, "source %s or sink %s widget weren't set up properly\n",
+			src_fw_module->man4_module_entry.name,
+			sink_fw_module->man4_module_entry.name);
+		return -ENODEV;
+	}
+
 	sroute->src_queue_id = sof_ipc4_get_queue_id(src_widget, sink_widget,
 						     SOF_PIN_TYPE_SOURCE);
 	if (sroute->src_queue_id < 0) {