[Vanilla] World Builder Crashing when loading map on mac

[Drama20J]

Hey, I was creating a map on World Builder. Saved it. Opened it again, and worked on it some more and saved it again. But then I started having crash problems. I would try to place a city and it would crash. I'd be able to load the map again and work more, but again, I would try to place a city and it would crash. Now it won't even load the map without crashing. I really don't want to lose this map and start over. Any help would be great. I'm on a mac btw. Thank you