Fix memory leak
diff --git a/src/mixer.c b/src/mixer.c
index c8480d7..94aa019 100644
--- a/src/mixer.c
+++ b/src/mixer.c
@@ -133,6 +133,8 @@
         free(grp->ctl);
     }
 
+    free(grp);
+
     mixer->is_card_info_retrieved = false;
 }