[MC-45009] Inventory and container empty/world corrupted after downgrading to older version.

Moderator Note

Downgrading from newer versions to older versions may have undesired behavior, please back up your worlds before testing snapshots.
Upgrading to a snapshot may also corrupt worlds, please back up your world before testing.

Enabling Development Builds Warning in the Launcher:

Are you sure you want to enable development builds?
They are not guaranteed to be stable and may corrupt your world.
You are advised to run this in a seperate directory or run regular backups.

Downgrading is not, was never and will never be officially supported!
Definition of downgrading: Going from a version with a higher number (example: 1.12.2) to a version with a lower number (example: 1.11)

[Mojang] Jeb (Jens Bergensten) in https://twitter.com/jeb_/status/507193706781614080

... Don't open a 1.8 world in 1.7 unless you have a backup ...

https://twitter.com/jeb_/status/507198150474727424

Since you ask: 1.7 doesn't know how to handle 1.8 saves, but tries its best not to crash. This means it ignores data, which is lost forever.

14w03a came up today and I noticed the transparancy bug with glass panes, so I switched back to 14w02c to verify that was working correctly there. All items everywhere vanished. Everything in my inventory, equipped gear, even everything in chests and furnaces are gone. Switching back to 14w03a did not bring it back.