RenderWindow was calling wrong Window constructor

Since commit https://github.com/LaurentGomila/SFML.Net/commit/62b70062549feee97123ee13735b634f5f88400f wrong Window constructor was called from RenderWindow

I believe it was just typing error in commit https://github.com/LaurentGomila/SFML.Net/commit/62b70062549feee97123ee13735b634f5f88400f because before adding Unicode it was already calling with 0(dummy argument) used by Window constructor to distinguish constructors for creating window from handle and constructor to just pass handle to ObjectBase.