fix bug in tools.scaffold
fix bug in tools.scaffold

AlexIljin/factor,kingcons/factor,dch/factor,tgunr/factor,seckar/factor,slavapestov/factor,erg/factor,mrjbq7/factor,bjourne/factor,seckar/factor,nicolas-p/factor,mrjbq7/factor,nicolas-p/factor,cataska/factor,ceninan/factor,tgunr/factor,ceninan/factor,mcandre/factor,bjourne/factor,kingcons/factor,mcandre/factor,AlexIljin/factor,sarvex/factor-lang,dch/factor,slavapestov/factor,factor/factor,sarvex/factor-lang,mcandre/factor,nicolas-p/factor,mcandre/factor,kingcons/factor,AlexIljin/factor,slavapestov/factor,cataska/factor,cataska/factor,slavapestov/factor,mcandre/factor,seckar/factor,factor/factor,factor/factor,AlexIljin/factor,bpollack/factor,erg/factor,bpollack/factor,tgunr/factor,erg/factor,sarvex/factor-lang,mrjbq7/factor,AlexIljin/factor,littledan/Factor,bjourne/factor,dch/factor,erg/factor,tgunr/factor,factor/factor,erg/factor,ceninan/factor,nicolas-p/factor,littledan/Factor,mcandre/factor,dch/factor,bjourne/factor,nicolas-p/factor,bjourne/factor,nicolas-p/factor,littledan/Factor,bpollack/factor,factor/factor,littledan/Factor,nicolas-p/factor,cataska/factor,AlexIljin/factor,bpollack/factor,slavapestov/factor,mcandre/factor,sarvex/factor-lang,dch/factor,sarvex/factor-lang,bjourne/factor,bpollack/factor,bjourne/factor,bpollack/factor,mrjbq7/factor,mrjbq7/factor,tgunr/factor,slavapestov/factor,erg/factor,bpollack/factor,tgunr/factor,ceninan/factor,slavapestov/factor,sarvex/factor-lang,erg/factor,AlexIljin/factor,dch/factor,mrjbq7/factor,factor/factor,sarvex/factor-lang,kingcons/factor