When uploading patches to review in review board and the project is hosted on github this happens:

* because git diff writes only a small part of the SHA1 by default this is recorded in the diff
* review board takes that part and tries to access the github API using only this info
* github offers an empty page with no HTTP error
* review board tries to apply a diff to an empty file, resulting in an error

Manual solution:
do a git diff with --full-index

Patch solution: if the diff doesn't contain the full index then throw an error

Tested at my organisation