config_file_helper: don't call Modules::find() for null module
config_file_helper: don't call Modules::find() for null module

Installer doesn't have Modules, so this should let us share the code a bit
more freely.

Might also avoid some unexpected results.

kelaskakap/cms-api-unggun,kelaskakap/cms-api-unggun,PeterRock/Ci-Bonfire3,PeterRock/Ci-Bonfire3,PeterRock/Ci-Bonfire3,kelaskakap/cms-api-unggun