[metacity] compositor: add error trap in free_win

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 69c73af07a9c7274d3203bb0363928ece4e55869
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Wed May 25 14:43:30 2016 +0300

    compositor: add error trap in free_win
    
    It seems that picture might be destroyed with window if it is
    created by passing window id as drawable to XRenderCreatePicture.
    
    Add error trap around XRenderFreePicture to avoid Metacity crash
    with RenderBadPicture error.
    
    https://bugs.launchpad.net/ubuntu/+source/metacity/+bug/1582687

 src/compositor/compositor-xrender.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/compositor/compositor-xrender.c b/src/compositor/compositor-xrender.c
index a9e1de4..364b6cd 100644
--- a/src/compositor/compositor-xrender.c
+++ b/src/compositor/compositor-xrender.c
@@ -1956,7 +1956,10 @@ free_win (MetaCompWindow *cw,
 
   if (cw->picture)
     {
+      meta_error_trap_push (display);
       XRenderFreePicture (xdisplay, cw->picture);
+      meta_error_trap_pop (display, FALSE);
+
       cw->picture = None;
     }