ITS#7146 check for ad_index overflow

Temporary fix...

servers/slapd/back-mdb/id2entry.c

@@ -569,6 +569,11 @@ static int mdb_entry_encode(Operation *op, Entry *e, MDB_val *data, Ecount *eh)
 	ptr = (unsigned char *)(lp + eh->offset);
 
 	for (a=e->e_attrs; a; a=a->a_next) {
+		if (a->a_desc->ad_index >= MDB_MAXADS) {
+			Debug( LDAP_DEBUG_ANY, "mdb_entry_encode: too many AttributeDescriptions used\n",
+				0, 0, 0 );
+			return LDAP_OTHER;
+		}
 		*lp++ = mdb->mi_adxs[a->a_desc->ad_index];
 		l = a->a_numvals;
 		if (a->a_nvals != a->a_vals)