 
     func fetchClasses() {
         userCourses.removeAll()
-        let uid = FIRAuth.auth()?.currentUser?.uid
-        FIRDatabase.database().reference().child("users").child(uid!).child("courses").observe(.childAdded, with: { (snapshot) in
+        guard let uid = FIRAuth.auth()?.currentUser?.uid else {
+            return
+        }
+        FIRDatabase.database().reference().child("users").child(uid).child("courses").observe(.childAdded, with: { (snapshot) in
             print(snapshot.value as! String)
             
             self.userCourses.append(snapshot.value as! String)

            perform(#selector(handleLogout), with: nil, afterDelay: 0)
        }
        userCourses.removeAll()
        fetchNotifications()
        fetchCurrentName()
        self.tableView.reloadData()
    }

    
    
    func fetchNotifications() {
        guard let uid = FIRAuth.auth()?.currentUser?.uid else {
            return
        }
        FIRDatabase.database().reference().child("users").child(uid).child("notifications").child("0").observe(.value, with: { (snapshot) in
            print(snapshot)
            //notificationSectionHeaders.append()
            
