Nil found while unwrapping an Optional value

I've been getting an error that says "Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value". Can someone please clarify what this error means, it appears around line let cell = tableView.dequeueReusableCell(withIdentifier: "MovieCell") as! MovieCell

import UIKit

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate { func tableView( _ tableView: UITableView, numberOfRowsInSection section: Int) -> Int{

    return movies.count
}

func tableView( _ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{
    
    let cell = tableView.dequeueReusableCell(withIdentifier: "MovieCell") as! MovieCell
    
    let movie = movies[indexPath.row]
    let title = movie["title"] as! String
    let synopsis = movie["overview"] as! String
    
    cell.titleLabel.text = title
    cell.synopsisLabel.text = synopsis
    
    return cell
    
}

@IBOutlet weak var tableView: UITableView!
var movies = [[String:Any]]()

override func viewDidLoad() {
    super.viewDidLoad()
    
    tableView.dataSource = self
    tableView.delegate = self
    
    // Do any additional setup after loading the view.
    
    print("Hello")
    
    let url = URL(string: "https://api.themoviedb.org/3/movie/now_playing?api_key=a07e22bc18f5cb106bfe4cc1f83ad8ed")!
    let request = URLRequest(url: url, cachePolicy: .reloadIgnoringLocalCacheData, timeoutInterval: 10)
    let session = URLSession(configuration: .default, delegate: nil, delegateQueue: OperationQueue.main)
    let task = session.dataTask(with: request) { (data, response, error) in
         // This will run when the network request returns
         if let error = error {
                print(error.localizedDescription)
         } else if let data = data {
                let dataDictionary = try! JSONSerialization.jsonObject(with: data, options: []) as! [String: Any]
             
             self.movies = dataDictionary["results"] as! [[String:Any]]
             
             self.tableView.reloadData()

             print(dataDictionary)
             
                // TODO: Get the array of movies
                // TODO: Store the movies in a property to use elsewhere
                // TODO: Reload your table view data

         }
    }
    task.resume()
}

}