Comment 2 for bug 850365

StacktraceTop:
 _cogl_push_framebuffers (draw_buffer=0x0, read_buffer=0x0) at ./cogl-framebuffer.c:1272
 pixbuf_to_cogl_handle (pixbuf=0x7f67d8202140, add_padding=<optimized out>) at st/st-texture-cache.c:819
 on_pixbuf_loaded (source=<optimized out>, result=<optimized out>, user_data=0x21d6710) at st/st-texture-cache.c:918
 g_simple_async_result_complete (simple=0x21e8520) at /build/buildd/glib2.0-2.29.90/./gio/gsimpleasyncresult.c:749
 complete_in_idle_cb_for_thread (_data=0x1af7f80) at /build/buildd/glib2.0-2.29.90/./gio/gsimpleasyncresult.c:816