[mutter] onscreen/native: Fix cast from CoglOnscreenEgl

[Marge Bot <marge-bot src gnome org>]

commit b962822f26452496c172e837e9c4d1d4d837f462
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Mar 8 11:07:58 2021 +0100

    onscreen/native: Fix cast from CoglOnscreenEgl
    
    It used the defunct platform pointer, meaning if this path would have
    hit, it'd end up with a segmentation fault due to the platform pointer
    being NULL.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1759>

 src/backends/native/meta-onscreen-native.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
---
diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index d35fefb16c..4290eeeca8 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -2032,8 +2032,7 @@ destroy_egl_surface (CoglOnscreen *onscreen)
   egl_surface = cogl_onscreen_egl_get_egl_surface (onscreen_egl);
   if (cogl_onscreen_egl_get_egl_surface (onscreen_egl) != EGL_NO_SURFACE)
     {
-      MetaOnscreenNative *onscreen_native =
-        cogl_onscreen_egl_get_platform (onscreen_egl);
+      MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
       MetaEgl *egl = meta_onscreen_native_get_egl (onscreen_native);
       CoglFramebuffer *framebuffer = COGL_FRAMEBUFFER (onscreen);
       CoglContext *cogl_context = cogl_framebuffer_get_context (framebuffer);