Fixed case where error in a describe at runtime caused busted to die.
Fixed case where error in a describe at runtime caused busted to die.

ryanplusplus/busted,leafo/busted,istr/busted,nehz/busted,azukiapp/busted,mpeterv/busted,sobrinho/busted,xyliuke/busted,DorianGray/busted,Olivine-Labs/busted,o-lim/busted