Undo after updating features creates an empty class

[harbortype (Henrique Beier)]

When I press Cmd+Z to undo right after I update the OpenType features, Glyphs creates an empty class called xxxx. Tested in builds 1141 and 1150. MacOS 10.13.5.

Here is a short screencast:

https://my.pcloud.com/publink/show?code=XZRBuf7ZTAmcgVpLvyQ0t2GuSbYCxjYQPUbk

[GeorgSeifert]

I fixed it.