Workflow variable not being recognized

We have an issue where when one of our workflow variables is "null" it's not being populated at all and the provisioning command fails. Is this a known bug? How do I pass a null value to the connector?

This has only been a problem on 7.1.1.161195

Query - Supposed to be null for type 'Employee'

Select user_id,
        end_date,
        to_CHAR(TO_DATE(End_date, 'MM/DD/YY HH24:mi'),'MM/DD/YY HH24:mi AM') as AFXCUSTOM_CUSTOM_ENDDATEAD
  from     PV_USERS
where user_id = '${access_request_cri_meu_userId}'
      and employee_type ='Contractor'

 Connector Mapping

Error

'org.mule.api.transformer.TransformerMessagingException: Unparseable date: "${Custom.Enddatead}" . Value of 'accountExipres' should be in 'MM/dd/yy HH:mm a' format. (java.lang.Exception). Message payload is of type: String'.  If available, another handler will be used to fulfill this item.

Workflow Variables