PARSE user still active after log-out - swift

Question

I'm learning to use Parse Server to manage users and passwords. I have an app that lets the user log-in and store information in the server (age, weight, gender and name). But I'm having a problem, if the user logs out, the app takes them to the login page and, if after that they use a non-existing user or incorrect password, after showing the alert "Incorrect user or password", the app takes them to the main page with the previous user information. I'm not sure what is going on; the code I'm using to log in is this:
#IBAction func signInButton(_ sender: Any) {
let acl = PFACL()
acl.getPublicWriteAccess = true
PFUser().acl = acl
if userTextField.text == "" || passwordTextField.text == "" {
createAlert(title: "Error", message: "Both fields should be filled")
} else {
activityIndicator = UIActivityIndicatorView(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
activityIndicator.center = self.view.center
activityIndicator.hidesWhenStopped = true
activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.gray
view.addSubview(activityIndicator)
activityIndicator.startAnimating()
UIApplication.shared.beginIgnoringInteractionEvents() // UIApplication.shared() is now UIApplication.shared
PFUser.logInWithUsername(inBackground: userTextField.text!, password: passwordTextField.text!, block: { (user, error) in
self.activityIndicator.stopAnimating()
UIApplication.shared.endIgnoringInteractionEvents() // UIApplication.shared() is now UIApplication.shared
if error != nil {
var displayErrorMessage = "Please try again later."
let error = error as NSError?
if let errorMessage = error?.userInfo["error"] as? String {
displayErrorMessage = errorMessage
}
self.createAlert(title: "Login Error", message: displayErrorMessage)
} else {
print("Logged in")
let usuario = PFUser.current()
let dataUse = self.queryDownload(usuario: usuario!)
for items in dataUse {
let dataMeassure: GlucoseEvents = NSEntityDescription.insertNewObject(forEntityName: "GlucoseEvents", into: DatabaseController.getContext()) as! GlucoseEvents
dataMeassure.allAtributes = items
}
DatabaseController.saveContext()
self.performSegue(withIdentifier: "goToMain", sender: self)
}
})
}
}
Now, this problem only happens after the logout, so I'm guessing the error in that function. The code of the logout is:
#IBAction func logOut(_ sender: Any) {
let refreshAlert = UIAlertController(title: "Confirm", message: "Really LogOut?", preferredStyle: UIAlertControllerStyle.alert)
refreshAlert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { (action: UIAlertAction!) in
PFUser.logOutInBackground { (error) in
if error != nil {
self.createAlert(title: "Error", message: "Error")
}
}
self.performSegue(withIdentifier: "closedProf", sender: self)
}))
refreshAlert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: { (action: UIAlertAction!) in
print("Handle Cancel Logic here")
}))
present(refreshAlert, animated: true, completion: nil)
}
Is there another way to logout and avoid this problem? Thanks
More info
So I tried to see if the problem was the server not returning a nil user. And added a print statement to the logout. Turns out that it's nil so I don't know why it is being stored (or where) but the LogOut returns a nil user.