Hey guys, in case you need a temporary fix for the gallery block fatal error while testing the Gutenberg plugin, here is a gist for you: https://gist.github.com/BicanMarianValeriu/f8e5f41a25f92e6c58cf64c7fdb01f14

It basically removes the server-side rendering that generates that error. This should be used as a temporary solution until a fix is provided.