When an image is missing in a file revision the api returns a broken image url for that revision. I guess it should either return a blank url field or no url field at all (or something) but not such a broken url.
In the example below the file is missing in the original revision but the api still returns the following for that revision's image url: https://upload.wikimedia.org/wikipedia/commons/archive/a/a7/
Example file:
https://commons.wikimedia.org/wiki/File:30th_Street_at_5th_Avenue_-_Stra%C3%9Fe_in_New_York.jpg