adds base64 decoding (fixes #5656)

fixes #5656
You have a trailing whitespace on this line (and a few other lines), and it makes our CI fail (on purpose, because many developers sees trailing whitespace as a poor sign of code quality).

If you type `mv .git/hooks/pre-commit.sample .git/hooks/pre-commit` at the root of your repository, you'll get a warning when trying to commit trailing whitespace in that local repository.