GitLab

The condition wasn't triggering so code wasn't being tested (). This applies to:
```
def f(vector[double] x):
  pass
```
which should now generate:
```
__pyx_v_a = __pyx_convert_vector_from_py_double(values[0]); if (unlikely(PyErr_Occurred())) __PYX_ERR(0, 5, __pyx_L3_error)
...
__pyx_r = __pyx_pf_4cnvt_f(__pyx_self, __PYX_STD_MOVE_IF_SUPPORTED(__pyx_v_a));
```

I haven't included any specific tests because I think it should be covered by the existing test-suite (now that it works) and it's only a performance improvement - it doesn't allow any new behaviour.

See https://github.com/cython/cython/issues/4163