Fix ITS#1239:

slapadd core-dumps when destroying db's env (Sleepycat 3.2.9) (ITS#1239)
Only call ldbm_shutdown_env if the database has been opened, ie. when
li->li_dbenv != NULL.  Would appear any time a shutdown occurred and
not all LDBM databases were opened.

servers/slapd/back-ldbm/init.c

@@ -218,7 +218,8 @@ ldbm_back_db_destroy(
 	/* should free/destroy every in be_private */
 	struct ldbminfo	*li = (struct ldbminfo *) be->be_private;
 
-	ldbm_shutdown_env(li->li_dbenv);
+	if (li->li_dbenv)
+	    ldbm_shutdown_env(li->li_dbenv);
 
 	free( li->li_directory );
 	attr_index_destroy( li->li_attrs );