Option id 'null' is not valid response from JIRA when madatory custom fields are not sent from ServiceNow (Jira Spoke)

WhenAdditional Fields from ServiceNow are mapped to JIRA Custom fields and if the value is not set from ServiceNow, JIRA end point may respond with the below error message:

Option id 'null' is not valid

The custom field is probably defined as mandatory on the JIRA end

Remove the mandatory field requirement on the JIRA end or make sure that the value is passed from the ServiceNow end .