userContent *zip* (all files in zip) stopped working at 2.164

When using the (all files in zip) functionality starting at 2.164, either from the UI or URL (https:/myjenkins/userContent/*zip*/image.zip), the resulting image.zip has no content. 

This has silently broken our builds, which utilize this functionality to retrieve certain content. Downgrading jenkins.war to 2.163 restores the functionality.