feat: retrying `getFile` requests upon empty file paths

This is the only correct way of handling this case. The auto-retry plugin or the files plugin should take care of this. They should then also adjust the return type of the method and guarantee `file_path` to be present.

Start by reading the auto-retry plugin and files plugin handling for getFile requests, then inspect the method's current return type. Done means empty file paths are retried by the appropriate plugin and the return type guarantees file_path is present.

Written by the indexing model from the issue text.