Loading pre 0.15 world crashes the game

So, I have an Nvidia Shield Tablet K1 and a Nexus 6 phone. On both of my devices, when I try to use a world that I used BEFORE I updated to 0.15.0, I go into the world, and it just crashes! This bug is really bad, please fix it as soon as possible. When ever the betas come out, I always test them on my survival world that I've had for years, but for some reason this time it's not working. If you need a video of it or any further information, contact me on twitter. @CSMineManYT

P.S. I can't really include a screenshot because the screenshot would just say it crashed...