Well, IIRC Igno is unable to play right now, so that avatar is on the way out if you don't save him.

If you have him sally you can do as much damage as possible, then pull all his men back inside the walls and exit the battle for a 'successful' sally, even if you don't drive off all the Hungarians. Then you'll be sitting next to the walls to command the defense if what's left of the Hungarians decides to make their assault.