like button like instgram crash after press : i added new option to my app the user can like the places but when i press on the like button i get crash and this is my code

tableview cell button

    @IBAction func likePressed(_ sender: Any) {
        self.likeBtn.isEnabled = false
        let ref = Database.database().reference()
        //let key = ref.childByAutoId().key
        let keyToPost = ref.child("Restaurant").childByAutoId().key
        
        
        ref.child("Restaurant").child(self.postID).observeSingleEvent(of: .value, with: { (snapshot) in
                              //.child(self.id)
            if let post = snapshot.value as? [String : AnyObject] {
                let updateLikes: [String : Any] = ["peopleWhoLike/\(keyToPost)" : Auth.auth().currentUser!.uid]
                ref.child("Restaurant").child(self.postID).updateChildValues(updateLikes, withCompletionBlock: { (error, reff) in
                    
                    if error == nil {
                        ref.child("Restaurant").child(self.postID).observeSingleEvent(of: .value, with: { (snap) in
                            if let properties = snap.value as? [String : AnyObject] {
                                if let likes = properties["peopleWhoLike"] as? [String : AnyObject] {
                                    let count = likes.count
                                    self.likeLabel.text = "\(count) Likes this place"
                                    
                                    let update = ["likes" : count]
                                    ref.child("Restaurant").child(self.postID).updateChildValues(update)
                                    
                                    self.likeBtn.isHidden = true
                                    self.unlikeBtn.isHidden = false
                                    self.likeBtn.isEnabled = true
                                    print("Likes")
                                }
                            }
                        })
                    }
                })
            }
            
            
        })
        
        ref.removeAllObservers()
    }


some one can help me 
thank you