This is a patch of the 1.2.0 release with a few fixed regressions. For details you can check the blog post. If you find an issue, check the issue tracker and file a bug: it will be fixed in the 1.2.2 version.
The full changelog is here: Release 1.2.1 · crystal-lang/crystal · GitHub.
It might take a couple of days for the different packages to update.
Happy Crystalling!