[clutter] glx: Ignore ensuring context on NULL stages

[Emmanuele Bassi <ebassi src gnome org>]

commit 0b2073923206e3abfe328ed724328fa962c556ee
Author: Emmanuele Bassi <ebassi linux intel com>
Date:   Tue Jun 14 15:50:21 2011 +0100

    glx: Ignore ensuring context on NULL stages
    
    https://bugzilla.gnome.org/show_bug.cgi?id=652566

 clutter/glx/clutter-backend-glx.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/clutter/glx/clutter-backend-glx.c b/clutter/glx/clutter-backend-glx.c
index 76f48ee..1894030 100644
--- a/clutter/glx/clutter-backend-glx.c
+++ b/clutter/glx/clutter-backend-glx.c
@@ -333,7 +333,13 @@ static void
 clutter_backend_glx_ensure_context (ClutterBackend *backend,
                                     ClutterStage   *stage)
 {
-  ClutterStageGLX *stage_glx =
+  ClutterStageGLX *stage_glx;
+
+  /* ignore ensuring the context on an empty stage */
+  if (stage == NULL)
+    return;
+
+  stage_glx =
     CLUTTER_STAGE_GLX (_clutter_stage_get_window (stage));
 
   cogl_set_framebuffer (COGL_FRAMEBUFFER (stage_glx->onscreen));