Missing argument 2 for slickgrid_node_form_pre_render()

No errors checking checkbox, but not uncheck...

Editing line 836 to function slickgrid_node_form_pre_render(&$form) and then no erros into log. But field always not updating, without errors in console...

Here is what update Post is showing:

{"status":true,"op":"update","errors":null,"updated":{"856":{"vid":"2941","value":"Lundi"}},"field_name":"field_day","field_id":"field_day_value","messages":[{"type":"status","message":"Product1 was updated succesfully."}]}

After testing, field is updated only if one or more chexboxes checked.
If field is empty (no checkboxes checked), the last value is showing and it do not update.

No problem with Selection List type cck fields. It seems the problem is caused by empty values with checkboxes and as nothing to do logged error message about missing argument.