shouldUpdateModel property Null safety
A test of whether or not your vm or converter function should run in
response to a State change. For advanced use only.
Some changes to the State of your application will mean your vm or
converter function can't produce a useful Model. In these cases, such as
when performing exit animations on data that has been removed from your Store,
it can be best to ignore the State change while your animation completes.
To ignore a change, provide a function that returns true or false.
If the returned value is true, the change will be applied.
If the returned value is false, the change will be ignored.
If you ignore a change, and the framework needs to rebuild the Widget,
the builder function will be called with the latest
by your vm or converter function.
@override final ShouldUpdateModel<St>? shouldUpdateModel;