Update 1.2.13/build 12

Build 12 was the 5th beta of Update 1.2.13, and was released on March 22, 2018.

So far it's described only by a tweet from Matt Gartzke:

Minecraft beta 1.2.13.12 has rolled out. Just some new back-end stuff to help us collect crash reports that required a client-side fix. No bug fixes to note. Thanks everyone for continuing to play and test!