Panic when using difftastic

[thvdveld]

difftastic panics when I try to use it with the following message:

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /home/thvdveld/.cargo/registry/src/github.com-1ecc6299db9ec823/tree_magic_mini-3.0.3/src/fdo_magic/builtin/init.rs:26:34

I think it panics when unwrapping an empty string after splitting it.

[logistic-bot]

I also had this problem on an unrelated project. #13 fixes it.