Search results are now processed through data processing by search
service. The result will be a SearchResult model from our domain. Also
SearchResult will execute new queries, e.g. from paginate widget,
through SearchService to apply data processing again.
Remove duplicate stub code to trait, to keep own logic and code clean.
This will be the case if you add a flexform to the plugin with no value.
Then an empty filter is configured and you will not be able to submit a
value for this filter.