avdevice/pulse_audio_common: Use av_freep(), avoid leaving stale pointers

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavdevice/pulse_audio_common.c

@@ -163,8 +163,8 @@ static void pulse_add_detected_device(PulseAudioDeviceList *info,
     return;
 
   fail:
-    av_free(new_device->device_description);
-    av_free(new_device->device_name);
+    av_freep(&new_device->device_description);
+    av_freep(&new_device->device_name);
     av_free(new_device);
 
 }