Lemmatiser fails on certain data

[proycon]

reported by Tess Dejaeghere:

thread 'main' panicked at 'computed lemma: OtherError("Rule does not match
current word (unable to find and remove suffix o)")',
/home/tessd/tessdlama/opt/cargo/registry/src/github.com-1ecc6299db9ec823/deepfrog-0.2.0/src/lib.rs:137
:97
note: run with RUST_BACKTRACE=1 environment variable to display a
backtrace

With bertje-nld.yml on the attached data:
does_not_work2.txt

[proycon]

When #8 is handled this should be fixed, I implemented the necessary fixes in sesdiff.