Different results for isEmpty() check on a polygon depending on a first constructor argument type

[alexey-m-ukolov]

Hi.
I don't know if it is intended or not (looks like a bug to me), but if we pass an array to the Polygon constructor, it is always gets marked as non empty, even if the array itself was.

But if we pass a CoordinateCollection, emptiness of a Polygon is determined based on it's content - empty collection results in an empty Polygon.

The fix is very easy but I'm not sure if I should submit a PR - maybe it's an expected behavior. And even if it isn't, the fix will break backward compatibility.