Error in ranger.unify()

[Novampe]

I tried to unify my binary classification rf model trained by ranger. There is an error
Warning message:
In Ops.factor(get("Prediction"), n) : ‘/’ not meaningful for factors
I don't know how to get rid of it and make my code run. Any idea about this error would be appreciated.

[mayer79]

Please add a minimal reproducible example.