[metacity] compositor: set cw->window to NULL in xrender_free_window

[Alberts Muktupāvels <muktupavels src gnome org>]

commit da0f8c8f9ecbee7d4409a40608708aee89a6c5fb
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Tue Oct 25 23:01:41 2016 +0300

    compositor: set cw->window to NULL in xrender_free_window

 src/compositor/compositor-xrender.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/compositor/compositor-xrender.c b/src/compositor/compositor-xrender.c
index 8dd722b..9590cff 100644
--- a/src/compositor/compositor-xrender.c
+++ b/src/compositor/compositor-xrender.c
@@ -3292,6 +3292,7 @@ xrender_free_window (MetaCompositor *compositor,
   if (cw == NULL)
     return;
 
+  cw->window = NULL;
   cw->attrs.map_state = IsUnmapped;
   cw->damaged = FALSE;