AppleWatch - "attempting to insert null" when calling WKInterfaceDevice addCachedImage

Calling WKInterfaceDevice addCachedImage (_: name :) to send an image from my iPhone app to the Apple Watch (where the extension can report an image to show it). The exception is the following:

2015-06-09 20:47:57.079 TimeInterval[20195:5186462] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object from objects[3]'

      

        
        
        
      

    

Various google and StackOverflow searches show that this has to do with using a shortcut to create an NSDictionary that does not allow traversal nil

. However, my code doesn't make a dictionary at all. Also, when the debugger breaks (breakpoint on exceptions), I check that the UIImage and NSString name I am passing is not exactly null.

Has anyone else seen this? Any idea why this is happening or how to fix it? Has anyone really used addCachedImage successfully? (Considering how the new AppleWatch is, who knows!)

My piece of code, if it helps:

func application(application: UIApplication, handleWatchKitExtensionRequest userInfo: [NSObject : AnyObject]?, reply: (([NSObject : AnyObject]!) -> Void)!) {
    if let info = userInfo {
        NSLog("watch kit request: %@", info)
        if let element = info["element"] as? String {
            //Request to render an element
            if element == "timer" {
                let timerView = NPProgressLabel(size: CGSizeMake(48, 48))
                timerView.text = info["value"] as! String
                timerView.progressPercent = (info["progress"] as! NSNumber).floatValue
                timerView.render()

                let device = WKInterfaceDevice.currentDevice()
                var success = false
                if let image = timerView.currentImage {
                    success = device.addCachedImage(image, name: timerView.currentImageName()) // <------- crashing here ----------
                } else {
                    NSLog("no image");
                }
                if !success {
                    NSLog("failed")
                } else {
                    NSLog("addCachedImage success")
                }
                reply(["imageName": timerView.currentImageName()])
            } else {
                reply(["error": "Unknown element"])
            }
            return
        }
    }
    reply(["error": "Bad request"])
}