So, when a user has linked a camera to a viewport, e.g., set a camera as a rendering camera, this line of code will make that camera inactive and default to the internal viewport camera.
Yep, that was the intent since the OP said they did not want a camera in the scene ("I need not to have this camera on the scene") but I may have misinterpreted the meaning. Not familiar with how 3dsMax handles its cameras.
Yeah, I figured that this was probably intentional, but I just wanted to clarify that it is a bit of an odd thing to do.