In version 1.2.12 you could lock yourself into sneak mode so you didn't have to worry about falling off the edge of tall builds even when going into your inventory.

In the 1.2.13 version you can not do that and it creates problems especially when building something and putting new material in your hot bar and causing you to fall to your death.

Having this feature removed makes building a real chore and I thought this was one of the best things in the world when I found out about it.