[gtk+] Win32: fix warning

[Paolo Borelli <pborelli src gnome org>]

commit c643d8b40219d86ebb2eb5a7810e59d7bc7b79f5
Author: Paolo Borelli <pborelli gnome org>
Date:   Mon Feb 22 21:20:18 2016 +0100

    Win32: fix warning

 gdk/win32/gdkdisplay-win32.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk/win32/gdkdisplay-win32.c b/gdk/win32/gdkdisplay-win32.c
index 1ef8c9e..6832cbc 100644
--- a/gdk/win32/gdkdisplay-win32.c
+++ b/gdk/win32/gdkdisplay-win32.c
@@ -266,7 +266,7 @@ _gdk_win32_display_open (const gchar *display_name)
 
   win32_display->screen = g_object_new (GDK_TYPE_WIN32_SCREEN, NULL);
 
-  _gdk_monitor_init (win32_display->screen);
+  _gdk_monitor_init (GDK_WIN32_SCREEN (win32_display->screen));
   _gdk_visual_init (win32_display->screen);
   _gdk_screen_init_root_window (GDK_WIN32_SCREEN (win32_display->screen));
   _gdk_events_init ();