fix: correct format for files loaded from url location
fix: correct format for files loaded from url location

Summary: Create a file object with no children for files loaded from data provider URL params.

Reviewed By: mlopezantequera

Differential Revision: D28933452

fbshipit-source-id: d88624c63567935fda6d9596467958676e40540f

mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM