[gtk+] W32: Add missing reference taking in gdk_device_virtual_grab()

[Руслан Ижбулатов <ruslanizhb src gnome org>]

commit 00b39e4a82401f407a2df2e2e35a18ede88b41ea
Author: Руслан Ижбулатов <lrn1986 gmail com>
Date:   Sat Oct 17 07:59:37 2015 +0000

    W32: Add missing reference taking in gdk_device_virtual_grab()
    
    https://bugzilla.gnome.org/show_bug.cgi?id=756160

 gdk/win32/gdkdevice-virtual.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk/win32/gdkdevice-virtual.c b/gdk/win32/gdkdevice-virtual.c
index 2ed341f..3a97285 100644
--- a/gdk/win32/gdkdevice-virtual.c
+++ b/gdk/win32/gdkdevice-virtual.c
@@ -269,7 +269,7 @@ gdk_device_virtual_grab (GdkDevice    *device,
          g_clear_object (&_gdk_win32_grab_cursor);
        }
 
-      _gdk_win32_grab_cursor = cursor;
+      _gdk_win32_grab_cursor = (cursor == NULL) ? NULL : g_object_ref (cursor);
 
       if (_gdk_win32_grab_cursor != NULL)
        SetCursor (GDK_WIN32_CURSOR (_gdk_win32_grab_cursor)->hcursor);