Not all filters have a format, which results in a warning.

This fixes a warning in ODM:
```
Warning: Missing argument 4 for ZF\Apigility\Doctrine\Server\Collection\Filter\ODM\AbstractFilter::typeCastField(), called in /vendor/zfcampus/zf-apigility-doctrine-server/src/ZF/Apigility/Doctrine/Server/Collection/Filter/ODM/NotEquals.php on line 20 and defined in /vendor/zfcampus/zf-apigility-doctrine-server/src/ZF/Apigility/Doctrine/Server/Collection/Filter/ODM/AbstractFilter.php on line 11
```