VM: make FACTOR_FOR_EACH not call .end() more than once
VM: make FACTOR_FOR_EACH not call .end() more than once

mrjbq7/factor,dch/factor,AlexIljin/factor,bpollack/factor,factor/factor,nicolas-p/factor,AlexIljin/factor,mrjbq7/factor,AlexIljin/factor,bjourne/factor,bpollack/factor,factor/factor,dch/factor,dch/factor,bjourne/factor,bjourne/factor,nicolas-p/factor,factor/factor,nicolas-p/factor,dch/factor,tgunr/factor,nicolas-p/factor,mrjbq7/factor,dch/factor,nicolas-p/factor,tgunr/factor,bpollack/factor,tgunr/factor,factor/factor,mrjbq7/factor,slavapestov/factor,bpollack/factor,AlexIljin/factor,slavapestov/factor,slavapestov/factor,factor/factor,slavapestov/factor,bpollack/factor,slavapestov/factor,tgunr/factor,slavapestov/factor,bpollack/factor,bjourne/factor,bjourne/factor,nicolas-p/factor,bjourne/factor,tgunr/factor,dch/factor,mrjbq7/factor,tgunr/factor,AlexIljin/factor,bjourne/factor,nicolas-p/factor,slavapestov/factor,AlexIljin/factor,AlexIljin/factor,mrjbq7/factor,bpollack/factor,factor/factor