When trading with Villagers, they are able to walk away which can end the trade prematurely.

What I expected to happen:
When trading with a villager, they should remain stationary

What actually happened:
They are able to wander off, which will close the trading window when they get far enough away.

Steps to Reproduce:

• Open the trading gui with a villager
• Wait until the villager wanders off
• Notice the trade gui will close

This was tested on a local map, with another player joined over a Wifi LAN.

Tested on Samsung TabPro SM-T520 on Android 4.4.2