Fix SDL2 crash when creating cursor

Enfoiré de REMqb

src/Nazara/Platform/SDL2/CursorImpl.cpp

@@ -24,7 +24,7 @@ namespace Nz
 			m_iconImage.GetWidth(),
 			m_iconImage.GetHeight(),
 			32,
-			32 * m_iconImage.GetWidth(),
+			4 * m_iconImage.GetWidth(),
 			SDL_PIXELFORMAT_BGRA8888
 		);