If the `default_doi_resolver` and `use_default_settings` are used together searx crashes. (cherry picked from commit 2a90b3329b18fadf35bf79966cd2330d83547b7e)
If the `default_doi_resolver` and `use_default_settings` are used together searx crashes. (cherry picked from commit 2a90b3329b18fadf35bf79966cd2330d83547b7e)