[FormBuilderDropdown]: silently ignores an unknown initialValue

[grundid]

Is there an existing issue for this?

• [X] I have searched the existing issues

Package/Plugin version

9.2.1

Platforms

• [X] Android
• [X] iOS
• [X] Linux
• [X] MacOS
• [X] Web
• [X] Windows

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Minimal code example

 FormBuilderDropdown(
                      name: 'weekday',
                      decoration: InputDecoration(
                        labelText: 'Weekday',
                      ),
                      initialValue: DateTime.sunday,
                      allowClear: false,
                      validator: FormBuilderValidators.compose(
                        [FormBuilderValidators.required()],
                      ),
                      items: [
                        DropdownMenuItem<int>(
                          value: DateTime.monday,
                          child: Text("Monday"),
                        )
                      ])

Current Behavior

The dropdown shows an empty entry but still keeps the value in the state. When the user saves the form the value is returned as a valid selection.

Expected Behavior

The dropdown should fail as per design if an unknown option is given.

Steps To Reproduce

see minimal code example

Aditional information

No response