Merge pull request #1268 from agent3bood/fix/DateTimePicker_setState

fix: check mounted after async

Author: deandreamatias

lib/src/fields/form_builder_date_time_picker.dart

@@ -309,6 +309,7 @@ class _FormBuilderDateTimePickerState extends FormBuilderFieldDecorationState<
       default:
         throw 'Unexpected input type ${widget.inputType}';
     }
+    if (!mounted) return null;
     final finalValue = newValue ?? currentValue;
     didChange(finalValue);
     return finalValue;