greatCircle calculator return NAN while calculating distance between same coordinates 

```
$distance = GeoTools::distance()
    ->setFrom(new Coordinate([-23.3593208, 119.7350342]))
    ->setTo(new Coordinate([-23.3593208, 119.7350342]))
    ->in('km')
    ->greatCircle()

echo $distance //NAN
```

Using `haversine()` will return 0.0 which is the excepted behavior. 

version: 0.8.3
