[ Solved] Contract violation, Date Null

Good morning,

I asked this question on the French bonita forum but with no answer, I try now with the English community, forgive my English please :d.

I use a form to recover some data and a deadline date that the user CAN indicate.

This date is not mandatory, the datepicker is displayed only if a radio button is selected.

The problem now is that that the DatePicker widget starts by default on the current date, the variable "deadline" is instantiated by default to null in the Input JSON. Now, if no date is specified by the user, an error message appears:

error: { "exception": "class org.bonitasoft.engine.bpm.contract.ContractViolationException", "message": "Exception while Validating constraints", "Explanations": []}

In other words, the contract refuses to pick a null value, yet it is possible to manually put a null in the table.

I don't know how to solve my problem, Any help would be appreciated,

Thank you !