[gtk+] win32: do not use g_clear_pointer also on the clipboard window

[Ignacio Casal Quinteiro <icq src gnome org>]

commit d74a08b80f54e018bc3141849e3d0fbbf6f583b0
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Fri Nov 13 12:58:45 2015 +0100

    win32: do not use g_clear_pointer also on the clipboard window
    
    A follow up on the previous patch. We should use DestroyWindow
    directly since it has a different calling convention than
    the expected callback for g_clear_pointer

 gdk/win32/gdkdisplay-win32.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/gdk/win32/gdkdisplay-win32.c b/gdk/win32/gdkdisplay-win32.c
index 620dfe7..b9897c0 100644
--- a/gdk/win32/gdkdisplay-win32.c
+++ b/gdk/win32/gdkdisplay-win32.c
@@ -720,8 +720,12 @@ gdk_win32_display_dispose (GObject *object)
       display_win32->hwnd = NULL;
     }
 
-  g_clear_pointer (&display_win32->clipboard_hwnd, (GDestroyNotify)DestroyWindow);
-  _hwnd_next_viewer = NULL;
+  if (display_win32->clipboard_hwnd != NULL)
+    {
+      DestroyWindow (display_win32->clipboard_hwnd);
+      display_win32->clipboard_hwnd = NULL;
+      _hwnd_next_viewer = NULL;
+    }
 
   G_OBJECT_CLASS (gdk_win32_display_parent_class)->dispose (object);
 }