[libpanel] action-muxer: fix cast warning on Clang

[Christian Hergert <chergert src gnome org>]

commit cee426cdc01eab03a395bb72e422f9c67d15ac0a
Author: Christian Hergert <christian hergert me>
Date:   Wed Sep 14 14:10:44 2022 -0700

    action-muxer: fix cast warning on Clang

 src/panel-action-muxer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/panel-action-muxer.c b/src/panel-action-muxer.c
index 7d85e44..3157606 100644
--- a/src/panel-action-muxer.c
+++ b/src/panel-action-muxer.c
@@ -185,7 +185,7 @@ panel_action_muxer_list_groups (PanelActionMuxer *self)
       g_array_append_val (ar, prefix);
     }
 
-  return (char **)g_array_free (ar, FALSE);
+  return (char **)(gpointer)g_array_free (ar, FALSE);
 }
 
 static void
@@ -481,7 +481,7 @@ panel_action_muxer_list_actions (GActionGroup *group)
       g_clear_pointer (&action_names, g_strfreev);
     }
 
-  return (char **)g_array_free (ar, FALSE);
+  return (char **)(gpointer)g_array_free (ar, FALSE);
 }
 
 static gboolean