Bonita process execution

Hello community,

I am working on a mission management process and I have already created: my BPMN diagram, my business data model, my business variable. Now I have created an instantiation contract on my pool so that at the execution of the pool the user in charge of planning a mission fills in the form then goes to his superior in charge of validating the planned mission. My contract at the beginning of the execution does not take into account the mission fees (since the one in charge of planning a mission is not the one who decides the mission fees).

Now when I execute the process and fill in the form created by my contract and validate, it returns an error saying:

USERNAME=walter.bates | org.bonitasoft.engine.commons.exceptions.SRetryableException: javax.persistence.PersistenceException: org.hibernate.PropertyValueException: not-null property references a null or transient value : com.company.model.MissionManagement.mission_fees

I think that the problem comes from the fact that there is no value for the mission fees and in my starting contract defined on the pool the mission fees field is not present because the mission planning actor is not the one who decides the mission fees.

How do I tell my process that at the beginning the mission costs are not taken into account?

I hope I have formulated my concerns correctly. Please help.

Thank.