A repeatable bug that crashed foldit.
 Foldit crashed when there was no selected residues, Did not crash when there is a select residue have been picked before pushing done.
I have attached a log from the crash. The Log is from the sixth crash.

How i did it
click - cookbook
click - open recipe editor
In new recipe
click - Local wiggle
Add residues -  by stride
(Residues by stride start)   Add a residue
user pick <res 1>
(step) Add integer 1
(for) Add integer 25
Run
(Message about you have selected zero Residues currently)
Done  (Click done without clicking on a piece)
Crash