[gnome-panel] clock: fix cast-function-type warning

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 6c34cbe26925b7ed4fe1fd0269519f9a7c5edf65
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Tue Sep 11 14:23:53 2018 +0300

    clock: fix cast-function-type warning

 modules/clock/calendar-window.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
---
diff --git a/modules/clock/calendar-window.c b/modules/clock/calendar-window.c
index 05cc988a5..c0f83bcdc 100644
--- a/modules/clock/calendar-window.c
+++ b/modules/clock/calendar-window.c
@@ -1284,6 +1284,13 @@ constrain_list_size (GtkWidget      *widget,
         gtk_widget_set_size_request (widget, width, height);
 }
 
+static void
+constraint_data_free (ConstraintData *constraint,
+                      GClosure       *closure)
+{
+  g_free (constraint);
+}
+
 static void
 setup_list_size_constraint (GtkWidget *widget,
                             GtkWidget *calendar,
@@ -1297,7 +1304,7 @@ setup_list_size_constraint (GtkWidget *widget,
 
         g_signal_connect_data (widget, "size-allocate",
                                G_CALLBACK (constrain_list_size), constraint,
-                               (GClosureNotify) g_free, 0);
+                               (GClosureNotify) constraint_data_free, 0);
 }
 
 #endif /* HAVE_EDS */