How to fix “nw_connection_receive_internal_block_invoke” (console)

I was getting the same error. My code looked like this:

UserServices().getUserWithUID(uid: user.uid) { (user) in
    self.window?.rootViewController = MapViewController(user: user)
    self.window?.makeKeyAndVisible()
}

All I did to resolve the problem was change my code to this:

let userServices = UserServices()
userServices.getUserWithUID(uid: user.uid) { (user) in
    self.window?.rootViewController = MapViewController(user: user)
    self.window?.makeKeyAndVisible()
}

and the console errors disappeared.