Latest neuralcoref causes core dump

Shortest code to replicate:

```
import en_core_web_lg
import neuralcoref

nlp = en_core_web_lg.load()
neuralcoref.add_to_pipe(nlp)
text ="""
Donald Trump was released from Walter Reed Hospital. 
He is back to being careless as usual.
Doctors at Walter Reed can't do anything about it. """
doc = nlp(text)
```