em28xx-alsa: Fix error patch for init/fini

If something bad happens during init, we free the card data.
However, we still keep it initialized, causing some dependent
code to be called at .fini.

Fix it.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
diff --git a/drivers/media/usb/em28xx/em28xx-audio.c b/drivers/media/usb/em28xx/em28xx-audio.c
index 1563f71..45bea1ad 100644
--- a/drivers/media/usb/em28xx/em28xx-audio.c
+++ b/drivers/media/usb/em28xx/em28xx-audio.c
@@ -948,6 +948,7 @@
 
 card_free:
 	snd_card_free(card);
+	adev->sndcard = NULL;
 
 	return err;
 }
@@ -966,12 +967,12 @@
 
 	em28xx_info("Closing audio extension");
 
-	snd_card_disconnect(dev->adev.sndcard);
-	flush_work(&dev->wq_trigger);
-
-	em28xx_audio_free_urb(dev);
-
 	if (dev->adev.sndcard) {
+		snd_card_disconnect(dev->adev.sndcard);
+		flush_work(&dev->wq_trigger);
+
+		em28xx_audio_free_urb(dev);
+
 		snd_card_free(dev->adev.sndcard);
 		dev->adev.sndcard = NULL;
 	}