fix critical bug with not writing out `return void` leading to endless loops :-P
fix critical bug with not writing out `return void` leading to endless loops :-P

hughperkins/coriander,hughperkins/coriander,hughperkins/coriander,hughperkins/cuda-on-cl,hughperkins/coriander,hughperkins/cuda-on-cl,hughperkins/cuda-on-cl,hughperkins/cuda-on-cl