Error when create contact with PHP SDK

Hello,

I am facing strange issue, when I create new contact using PHP SDK it catches an exception but the contact is created on Infusionsoft with all the correct data. This happens when I try to push null for custom field defined as Date & Time.

I get the following error:
Server error: PATCH https://api.infusionsoft.com/crm/rest/v1/contacts/xxxx?access_token=xxxxxx resulted in a `500 Internal Server Error