InputDatePickerFormField should allow empty dates without 'Invalid format' message. #117511
Description
Use case
When using an InputDatePickerFormField to get a date in a form, the 'Invalid format' message is displayed. However, the form application might accept that the date input stays empty. In such occasions, the 'Invalid format' message should not be displayed.
Proposal
Add the 'acceptEmptyDate' field to InputDataPIckerFormField, like implemented in this fork's commit.
This must be provided by flutter directly.