If there’s no file in a report, then most probably there will be no measure at all, so indeed you won’t be able to set a quality gate on any metric.
May I ask you why you need to specify such condition on project without file ?
Because the quality gate is used to ensure the quality of your project is on the right path, but if there’s no file, then there’s no code, then there’s no quality, then there’s nothing to check.