Fix errors when filter does not exist

[KaulSe]

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The application throws an error when supplying an invalid filter key in the URL. The appropriate action would be to ignore the invalid filter key.

Steps to reproduce

1. You have a table
2. You supply an invalid filter. For example, it is possible to accomplish that by changing the filter key in the URL. An example: http://localhost:8000/dashboard?table[filters][invalid-filter]=test.
3. You now see an error.

Errors it fixes

1. Rappasoft\LaravelLivewireTables\DataTableComponent::Rappasoft\LaravelLivewireTables\Traits\Helpers\{closure}(): Argument #1 ($filter) must be of type Rappasoft\LaravelLivewireTables\Views\Filter, null given, called in /..../src/Illuminate/Collections/Traits/EnumeratesValues.php on line 780
2. Error: Call to a member function isEmpty() on null: /..../src/Traits/ComponentUtilities.php:97

I expect that the application does not accept invalid filters (filters not defined in filters()) and doesn't error on such input.

This PR fixes this behavior.

[KaulSe]

Ready for review :).