[Pharo-dev] AbstractNautilusUI "error, should not happen" from LayoutEmptyScope(LayoutAbstractScope)>>rebase:to:

In build 40239, if I try to add an instance variable (e.g. 'xx') to AbstractNautilusUI, I get "Error: should not happen" from LayoutEmptyScope(LayoutAbstractScope)>>rebase:to: A tried a few other classes and they are okay. I've tracked this down to occur since build 40147... 13697 Yet another cleanup of MessageBrowser API https://pharo.fogbugz.com/f/cases/13697 13698 Small cleanup of Model and the UI package https://pharo.fogbugz.com/f/cases/13698 13696 Nautilus Refactoring 1: Classlist widget https://pharo.fogbugz.com/f/cases/13696 Is this a known problem? I can't identify a ticket on the tracker. cheers -ben