Error inserting data

+----------------------+--------------+------+-----+---------+-------+
| Field                | Type         | Null | Key | Default | Extra |
+----------------------+--------------+------+-----+---------+-------+
| bookingStayId        | varchar(20)  | NO   | PRI | NULL    |       |
| bookingRoomNum       | int(8)       | NO   | PRI | NULL    |       |
| multiRoomNumber      | int(8)       | NO   | PRI | 0       |       |

Primary key multiRoomNumber with default value as 0 is seen as empty.
This leads to an outofmemory.

db/sql/mapper.php

@@ -447,7 +447,7 @@ function insert() {
 			if ($field['pkey']) {
 				$field['previous']=$field['value'];
 				if (!$inc && $field['pdo_type']==\PDO::PARAM_INT &&
-					empty($field['value']) && !$field['nullable'])
+					is_null($field['value']) && !$field['nullable'])
 					$inc=$key;
 				$filter.=($filter?' AND ':'').$this->db->quotekey($key).'=?';
 				$nkeys[$nctr+1]=[$field['value'],$field['pdo_type']];