[at-spi2-core] Fix a crash

[Mike Gorse <mgorse src gnome org>]

commit 8ab9b272e4e2f6f7abe782c708c586f2ef8f8ad2
Author: Mike Gorse <mgorse novell com>
Date:   Tue Feb 1 09:36:18 2011 -0600

    Fix a crash

 atspi/atspi-accessible.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/atspi/atspi-accessible.c b/atspi/atspi-accessible.c
index 2dfb2ed..1b1c967 100644
--- a/atspi/atspi-accessible.c
+++ b/atspi/atspi-accessible.c
@@ -1344,6 +1344,7 @@ _atspi_accessible_add_cache (AtspiAccessible *accessible, AtspiCache flag)
   AtspiCache mask = accessible->parent.app->cache;
 
   if (mask == ATSPI_CACHE_UNDEFINED &&
+      accessible->parent.app->root &&
       accessible->parent.app->root->accessible_parent)
   {
     AtspiAccessible *desktop = atspi_get_desktop (0);