[gtk+] win32: do not use g_clear_pointer to destroy the window

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 2ad243d43db6e72ed64e24af8d350c00ea630a51
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Fri Nov 13 12:54:54 2015 +0100

    win32: do not use g_clear_pointer to destroy the window
    
    DestroyWindow expects a different calling convenction so
    we endup getting an error at runtime

 gdk/win32/gdkdisplay-win32.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/gdk/win32/gdkdisplay-win32.c b/gdk/win32/gdkdisplay-win32.c
index 7b1fbd8..620dfe7 100644
--- a/gdk/win32/gdkdisplay-win32.c
+++ b/gdk/win32/gdkdisplay-win32.c
@@ -714,7 +714,12 @@ gdk_win32_display_dispose (GObject *object)
 {
   GdkWin32Display *display_win32 = GDK_WIN32_DISPLAY (object);
 
-  g_clear_pointer (&display_win32->hwnd, (GDestroyNotify)DestroyWindow);
+  if (display_win32->hwnd != NULL)
+    {
+      DestroyWindow (display_win32->hwnd);
+      display_win32->hwnd = NULL;
+    }
+
   g_clear_pointer (&display_win32->clipboard_hwnd, (GDestroyNotify)DestroyWindow);
   _hwnd_next_viewer = NULL;