showBluetoothAccessoryPicker does not show up

I made up my own iAP2-BT-device, which is perfectly running by use the BT-list and the External Accessory Framework.

Now, following the instruction for MFI developers, I would like to show the showBluetoothAccessoryPicker using the following swift code:

EAAccessoryManager.shared().showBluetoothAccessoryPicker(withNameFilter: nil) { (error) in
            if let error = error {
                switch error {
                case EABluetoothAccessoryPickerError.alreadyConnected:
                    break
                default:
                    break
                }
            }
        }

Wherever I put this snipple in my app code the picker is never shown (device unpaired by "forget device") and I always get the console message: A constraint factory method was passed a nil layout anchor.  This is not allowed, and may cause confusing exceptions. Break on BOOL _NSLayoutConstraintToNilAnchor(void) to debug.  This will be logged only once.  This may break in the future.

I have no idea what to do to get this picker shown ...
Thanks for your help