Attempting to remove array values from a multivaluated attribute through the webservice removes all values

When using https://rest-api.fusiondirectory.info/#operation/deleteAttributeValues on a complex multivaluated attribute which uses arrays as values, such as dnsRecords, all values are removed.

This is because the code calls array_remove_entries which uses array_diff which only knows how to deal with stringable values. When called on arrays it trigger array to string conversion warnings.

So either we fix array_remove_entries to be able to work on arrays values, or we change the webservice code. In both cases we should make sure that array_remove_entries crashes out instead of returning an empty array to avoid data loss.