Fix #130 by using isReferenceToReference helper method

[alshain]

This should fix #130 by using isReferenceToReference which first does a null check on the result of r.resolve()

[stickler-ci]

I couldn't find a .stickler.yml file in this repository. I can make one for you, or you can create one by following the documentation.

[AntoniRokitnicki]

@alshain I have merged your PR to my fork