[gtk+] gesture: Fix gcc constness warning

[Benjamin Otte <otte src gnome org>]

commit 38d8fa0b6a07d31bc84ebe79759933f6fe261f00
Author: Benjamin Otte <otte redhat com>
Date:   Thu Dec 14 03:01:00 2017 +0100

    gesture: Fix gcc constness warning

 gtk/gtkgesture.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkgesture.c b/gtk/gtkgesture.c
index 53cc0a0..b34c4dd 100644
--- a/gtk/gtkgesture.c
+++ b/gtk/gtkgesture.c
@@ -531,7 +531,7 @@ _gtk_gesture_update_point (GtkGesture     *gesture,
   if (data->event)
     g_object_unref (data->event);
 
-  data->event = g_object_ref (event);
+  data->event = g_object_ref ((gpointer) event);
   _update_touchpad_deltas (data);
   _update_widget_coordinates (gesture, data);