fix assertion failure in sndio audio caused by the recent hotplugging support

src/audio/sndio/SDL_sndioaudio.c

@@ -350,6 +350,13 @@ SNDIO_Deinitialize(void)
     UnloadSNDIOLibrary();
 }
 
+static void
+SNDIO_DetectDevices(void)
+{
+	SDL_AddAudioDevice(SDL_FALSE, DEFAULT_OUTPUT_DEVNAME, NULL, (void *) 0x1);
+	SDL_AddAudioDevice(SDL_TRUE, DEFAULT_INPUT_DEVNAME, NULL, (void *) 0x2);
+}
+
 static int
 SNDIO_Init(SDL_AudioDriverImpl * impl)
 {
@@ -366,6 +373,7 @@ SNDIO_Init(SDL_AudioDriverImpl * impl)
     impl->CaptureFromDevice = SNDIO_CaptureFromDevice;
     impl->FlushCapture = SNDIO_FlushCapture;
     impl->Deinitialize = SNDIO_Deinitialize;
+    impl->DetectDevices = SNDIO_DetectDevices;
 
     impl->AllowsArbitraryDeviceNames = 1;
     impl->HasCaptureSupport = SDL_TRUE;