# reduce() for fraction field elements

I am having an issue with the `reduce()`

method for `FractionFieldElement`

.
In a Jupyter notebook I executed the following code

```
sage: S = FractionField(QQ['t'])
sage: S.inject_variables()
sage: R = PolynomialRing(FractionField(QQ['t']),'x',3)
sage: R.inject_variables()
sage: (((x0^2-x1^2)/(x0-x1)).reduce())
```

but this returned an object with `NoneType`

, rather than
a fraction field element or ring element. What am I doing wrong?