Swift index out of range when refreshing - swift

Question

so ive been tring to solve this on my own for a few hours now. When ever i pull to refresh its crashes saying index out of range. Some people say its because of removing the arrays data before getting it and all that but only confused me further
here is my code
#objc fileprivate func fetchPostsWithUser() {
houses.removeAll()
myJobs.removeAll()
let ref = Database.database().reference().child("posts")
ref.observeSingleEvent(of: .value, with: { (snapshot) in
guard let dictionaries = snapshot.value as? [String: Any] else { return }
dictionaries.forEach({ (key, value) in
guard let dictionary = value as? [String: Any] else { return }
var post = Post(dictonary: dictionary)
post.id = key
Database.database().reference().child(key).observeSingleEvent(of: .value, with: { (snapshot) in
if post.pickedUserId == Auth.auth().currentUser?.uid {
self.myJobs.append(post)
} else if post.hasPicked == true && post.pickedUserId != Auth.auth().currentUser?.uid {
print("taken out")
} else {
self.houses.append(post)
}
self.houses.sort(by: { (p1, p2) -> Bool in
return p1.creationDate.compare(p2.creationDate) == .orderedDescending
})
self.tableView.reloadData()
}, withCancel: { (err) in
print("Failed to fetch like info for post:", err)
})
})
}) { (err) in
print("Failed to fetch posts:", err)
}
}
A solution to this error will be greatly appreciated, thank you.