Android NotificationManager giving me "no valid small icon" error

You're actually not setting an icon for the push notification. Add .setSmallIcon(R.drawable.your_icon) to your notification.

 NotificationCompat.Builder notification = new NotificationCompat.Builder(this)
            .setContentTitle("New Password Request From " + (String) data.get("ip"))
            .setSmallIcon(R.drawable.your_icon)
            .addAction(acceptAction)
            .addAction(declineAction);

You have not called setSmallIcon() on the NotificationCompat.Builder. This provides the icon that will go in the status bar while the Notification is active.