Decompile and save all classes just hangs

Running on OS/X. There doesn't seem to be any feedback. menus no longer work. I have to eventually kill the app.

Start by reproducing the “Decompile and save all classes” action on OS/X and observe when feedback stops and menus become unusable. Trace whether the hang occurs during decompilation or saving; done means the operation completes or reports its progress and failure without requiring the app to be killed.

Written by the indexing model from the issue text.