This relates to Espresso v.9b3

Can anyone else confirm this: If you attempt to quit Espresso while you have a document open that you haven’t saved changes to, you will be prompted to either “Save”, “Don’t Save” or “Cancel”. Choosing “Don’t Save” will cause the app to hang and become unresponsive.

Yeah this is a known issue. Saving or closing the document before quitting should work fine until there is a fix.