Hi I was making an adventure map with custom villagers, and I made this villager trade air for air so that the player cant trade anything but when I open the GUI to make sure it trades air for air it crashes. I saw this before but it was for 1.7.2 and it was resolved however in that post the villager wasn't selling air for air
Steps to reproduce
1.type this command

/summon Villager ~ ~1 ~ {Offers:{Recipes:[{maxUses:1,buy:{id:0­,Count:1},sell:{id:0,Count:1}}]}}

2.Open his GUI