Firebase data to tableview, crash after appending data - swift

Question

I am trying to download data from Firebase using
firebaseDB.observe(DataEventType.value, with: { (snapshot) in })
which works well. I am able to receive the following data:
let fetchedObject = items.value as? [String: AnyObject]
let dbUrl = fetchedObject?["url"]
let dbTime = fetchedObject?["time"]
let dbStatus = fetchedObject?["status"]
Using print("\(dbUrl!), \(dbTime!), \(dbStatus!)"), I see the following output in the console:
https://google.de, 2019-04-26 07:44:54 +0000, new
However, because I want to show the data in a Tableview, I have created a swift file for a data model, called ItemModel with the following content:
class ItemModel {
var url: String?
var time: String?
var status: String?
init(url: String?, time: String?, status: String?){
self.url = url
self.time = time
self.status = status
}
}
When trying to populate the url, time and status using
let item = ItemModel(url: dbUrl as! String?, time: dbTime as! String?, status: dbStatus as! String?)
appending it with self.itemList.append(item), and reloading the table with self.tableViewOutlet.reloadData(), the app crashes.
If I comment out self.itemList.append(item), it does not crash.
What am I doing wrong? I am clearly missing something viable, but I just can't figure out what. I am really wondering why appending the data does not work... Thanks a lot for any help!
EDIT:
Complete fetching method:
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
var itemList = [ItemModel]()
override func viewDidLoad() {
super.viewDidLoad()
[...]
// Authenticate user
Auth.auth().signInAnonymously() {(authResult, error) in
if error == nil {
self.user = authResult!.user // Authenticate User
self.uid = self.user.uid // Users unique and anonymous identifier by Firebase
print(">> LOG: Auth success!")
// Download data from Firebase
var itemsDB: DatabaseReference!
itemsDB = Database.database().reference().child("somechild").child("someotherchild")
itemsDB.observe(DataEventType.value, with: { (snapshot) in
// Check if there is any relevant data
if snapshot.childrenCount > 0 {
// Initially clear the list
self.itemList.removeAll()
// Interate through all the values
for items in snapshot.children.allObjects as! [DataSnapshot] {
// Get the values from Firebase
let fetchedObject = items.value as? [String: AnyObject]
let dbUrl = fetchedObject?["url"]
let dbTime = fetchedObject?["time"]
let dbStatus = fetchedObject?["status"]
let item = ItemModel(url: dbUrl as? String, time: dbTime as? String, status: dbStatus as? String)
print("\(item.url!), \(item.time!), \(item.status!)")
self.itemList.append(item)
}
// Reload the Tableview
self.tableViewOutlet.reloadData()
}
})
} else {
print(">> LOG: Error when trying to authenticate: \(error!)")
}
}
}
}