Call card_destroy_callback() when an ALSA element is removed

src/alsa.c

@@ -811,12 +811,18 @@ static gboolean alsa_card_callback(
     printf("card_callback_error %d\n", err);
     exit(1);
   }
+
   if (snd_ctl_event_get_type(event) != SND_CTL_EVENT_ELEM)
     return 1;
 
   int numid = snd_ctl_event_elem_get_numid(event);
   unsigned int mask = snd_ctl_event_elem_get_mask(event);
 
+  if (mask == SND_CTL_EVENT_MASK_REMOVE) {
+    card_destroy_callback(card);
+    return 0;
+  }
+
   if (!(mask & (SND_CTL_EVENT_MASK_VALUE | SND_CTL_EVENT_MASK_INFO)))
     return 1;