Avoid attaching undefined .throw/.return keys to test iterator.
Avoid attaching undefined .throw/.return keys to test iterator.

rafaelstz/regenerator,liviuignat/regenerator,kittens/regenerator,facebook/regenerator,rafaelstz/regenerator,sebmck/regenerator,facebook/regenerator,juliocanares/regenerator,Jericho25/regenerator,juliocanares/regenerator,facebook/regenerator,liviuignat/regenerator,kittens/regenerator,RReverser/js-goto-transpiler,RReverser/js-goto-transpiler,sebmck/regenerator,Jericho25/regenerator