'The class PFUser must be registered with registerSubclass before using Parse.'

I've looked around and all the other answers do not work for me, I'm trying to query PFUser, but I keep getting an exception of 'The class PFUser must be registered with registerSubclass before using Parse.'

This is where the issue occurs:

override func collectionView(collectionView: JSQMessagesCollectionView!, avatarImageDataForItemAtIndexPath indexPath: NSIndexPath!) -> JSQMessageAvatarImageDataSource! {
    let message = messages[indexPath.item]
    if self.avatars[message.senderId] == nil {
        var imageView = JSQMessagesAvatarImage(placeholder: UIImage(named: "profile"))
        self.avatars[message.senderId] = imageView

        let user = users[message.senderId]!
        print(user)
        var parseAvatar = PFFile()

        PFUser.registerSubclass()
        let imageQuery = PFUser.query()
        imageQuery?.whereKey("objectId", equalTo: user.objectId!)
        imageQuery?.limit = 1

        imageQuery?.findObjectsInBackgroundWithBlock({ (images: [AnyObject]?, error: NSError?) -> Void in
            if imageQuery?.countObjects() == 0 {
                return
            } else {
                for image in images! {
                    if image.objectForKey("profileImage") == nil {
                        return
                    } else {
                        let userPic = image.objectForKey("profileImage") as! PFFile
                        userPic.getDataInBackgroundWithBlock({ (imageData: NSData?, error: NSError?) -> Void in
                            if (error == nil) {
                                let image = UIImage(data: imageData!)
                                imageView.avatarImage = JSQMessagesAvatarImageFactory.circularAvatarImage(UIImage(data: imageData!), withDiameter: 30)
                            }
                        })
                    }

                }
            }
        })

            // Reload entire table now that the avatar is downloaded
            self.collectionView?.reloadData()

        }

    return self.avatars[message.senderId]
}

Any idea what I might be missing here? I did this in another file, and it doesn't have that issue. So I'm a little confused.

EDIT:

Like this?

import Foundation
import Parse

class TradeUser : PFUser {

override class func initialize() {
    self.registerSubclass()
}

var userID : String {
    get {return objectForKey("objectId") as! String}
    set { setObject(newValue, forKey: "objectId") }
}

var emailAddress : String {
    get {return objectForKey("email") as! String}
    set { setObject(newValue, forKey: "email") }
}

var firstName : String {
    get {return objectForKey("firstName") as! String}
    set {setObject(newValue, forKey: "firstName")}
}

var lastName : String {
    get {return objectForKey("lastName") as! String}
    set {setObject(newValue, forKey: "lastName")}
}

var primaryQueue : String {
    get {return objectForKey("primaryQueue") as! String}
    set {setObject(newValue, forKey: "primaryQueue")}
}

var image : PFFile {
    get { return self["profileImage"] as! PFFile }
    set { self["profileImage"] = newValue }
}

}

It seems like there's an issue with how the subclass is being registered.

Update your PFUser subclass with the following

class TradeUser : PFUser {

    override class func initialize() {
        struct Static {
            static var onceToken : dispatch_once_t = 0;
        }
        dispatch_once(&Static.onceToken) {
            self.registerSubclass()
        }
    }

    ...
}