`Field.subspace` sometimes fails for a global cyclic subspace

At v3.16.2, `Field.subspace` sometimes fails for a global cyclic subspace:
```python
>>> import cf
>>> f = cf.example_field(0)
>>> f.subspace(X=cf.wi(-180, 180))  # OK
<CF Field: specific_humidity(latitude(5), longitude(8)) 1>
>>> f.subspace(X=cf.wi(-170, 170))  # NOT OK: should give same result as [-180, 180]
ValueError: No indices found from: X=<CF Query: (wi [-170, 170])>
```
