avutil/opt: add missing case for AV_OPT_TYPE_CHLAYOUT in av_opt_free()

Fixes potential memleaks for existing options of this type.

Signed-off-by: James Almer <jamrial@gmail.com>

libavutil/opt.c

@@ -1729,6 +1729,10 @@ void av_opt_free(void *obj)
             av_dict_free((AVDictionary **)(((uint8_t *)obj) + o->offset));
             break;
 
+        case AV_OPT_TYPE_CHLAYOUT:
+            av_channel_layout_uninit((AVChannelLayout *)(((uint8_t *)obj) + o->offset));
+            break;
+
         default:
             break;
         }