Fix bug in find_primroot
Fix bug in find_primroot

Candidate might start at 0, which causes a mod by 0, which causes a
floating point exception, which causes crash.

3L3N4/zmap,shakenetwork/zmap,cicku/zmap,djeraseit/zmap,willscott/zmap,zmap/zmap,tdi/zmap,potatozhao/zmap,unixfreaxjp/zmap,scarito/zmap,djeraseit/zmap,KeelanArrendale/zmap,scarito/zmap-android,scarito/zmap-android,scarito/zmap-android,3L3N4/zmap,cicku/zmap,coolacid/zmap,potatozhao/zmap,unixfreaxjp/zmap,djeraseit/zmap,coolacid/zmap,3L3N4/zmap,eacha/zmap,willscott/zmap,BobuSumisu/zmap,tdi/zmap,3L3N4/zmap,coolacid/zmap,shakenetwork/zmap,shakenetwork/zmap,eacha/zmap,BobuSumisu/zmap,willscott/zmap,shakenetwork/zmap,BobuSumisu/zmap,scarito/zmap-android,BobuSumisu/zmap,scarito/zmap,tdi/zmap,zhuyue1314/zmap,unixfreaxjp/zmap,shakenetwork/zmap,potatozhao/zmap,KeelanArrendale/zmap,eacha/zmap,zhuyue1314/zmap,tdi/zmap,KeelanArrendale/zmap,BobuSumisu/zmap,KeelanArrendale/zmap,scarito/zmap,unixfreaxjp/zmap,zhuyue1314/zmap,cicku/zmap,cicku/zmap,coolacid/zmap,zhuyue1314/zmap,coolacid/zmap,tdi/zmap,3L3N4/zmap,eacha/zmap,KeelanArrendale/zmap,willscott/zmap,zmap/zmap,scarito/zmap,cicku/zmap,zmap/zmap,willscott/zmap,djeraseit/zmap,djeraseit/zmap,unixfreaxjp/zmap,potatozhao/zmap,scarito/zmap,zhuyue1314/zmap,potatozhao/zmap,eacha/zmap