PDOException: SQLSTATE[HY000]: General error: 1366 Incorrect integer value

Hi,
1.create a nodequeue
2. set 4 for "Queue size" field and save
3. after edit this nodequeue and remove 4 from "Queue size" field (no 0 (zero) just empty)
4. after save appear this error

PDOException: SQLSTATE[HY000]: General error: 1366 Incorrect integer value: '' for column 'size' at row 1: UPDATE {nodequeue_queue} SET name=:db_update_placeholder_0, title=:db_update_placeholder_1, subqueue_title=:db_update_placeholder_2, size=:db_update_placeholder_3, link=:db_update_placeholder_4, link_remove=:db_update_placeholder_5, owner=:db_update_placeholder_6, show_in_links=:db_update_placeholder_7, show_in_tab=:db_update_placeholder_8, show_in_ui=:db_update_placeholder_9, i18n=:db_update_placeholder_10, reverse=:db_update_placeholder_11, reference=:db_update_placeholder_12 WHERE (name = :db_condition_placeholder_0) ; Array ( [:db_update_placeholder_0] => homepage_slider [:db_update_placeholder_1] => Homepage slider [:db_update_placeholder_2] => [:db_update_placeholder_3] => [:db_update_placeholder_4] => [:db_update_placeholder_5] => [:db_update_placeholder_6] => nodequeue [:db_update_placeholder_7] => 0 [:db_update_placeholder_8] => 1 [:db_update_placeholder_9] => 1 [:db_update_placeholder_10] => 0 [:db_update_placeholder_11] => 0 [:db_update_placeholder_12] => 0 [:db_condition_placeholder_0] => homepage_slider ) in nodequeue_save() (line 841 of /sites/all/modules/contrib/nodequeue/nodequeue.module).

If I put 0 (zero) works fine, with empty field I take this error.