W/MediaRouter: Ignoring invalid provider descriptor: null

I keep getting this warning in the logs after we integrated the cast library into our app.

W/MediaRouter: Ignoring invalid provider descriptor: null

I traced this message to this line in MediaRouter.java; However I don't see why providerDescriptor is null.

    private void updateProviderContents(ProviderInfo provider,
            MediaRouteProviderDescriptor providerDescriptor) {
        if (provider.updateDescriptor(providerDescriptor)) {
            // Update all existing routes and reorder them to match
            // the order of their descriptors.
            int targetIndex = 0;
            boolean selectedRouteDescriptorChanged = false;
            if (providerDescriptor != null) {
                if (providerDescriptor.isValid()) {
   ...
                } else {
                    Log.w(TAG, "Ignoring invalid provider descriptor: " 
                    + providerDescriptor);
                }

In particular how should we act on this message?