Bug 711906 - ns-slapd segfaults using suffix referrals

https://bugzilla.redhat.com/show_bug.cgi?id=711906
Resolves: bug 711906
Bug Description: ns-slapd segfaults using suffix referrals
Reviewed by: nkinder (Thanks!)
Branch: master
Fix Description: Check node->mtn_be for NULL before dereferencing it
Platforms tested: RHEL6 x86_64
Flag Day: no
Doc impact: no

ldap/servers/slapd/mapping_tree.c

@@ -2905,7 +2905,7 @@ slapi_be_select( const Slapi_DN *sdn ) /* JCM - The name of this should change??
 {
     Slapi_Backend *be;
     mapping_tree_node *node= slapi_get_mapping_tree_node_by_dn(sdn);
-    if(node!=NULL)
+    if((node!=NULL) && (node->mtn_be!=NULL))
         be= node->mtn_be[0];
     else
         be = NULL;