Fix segfault bug in the kick command.
Fix segfault bug in the kick command.

This crash happens if you issue "kick N" in a tube with no buried jobs and
fewer than N delayed jobs while another tube has at least one delayed job.

potatosalad/beanstalkd,orangeholic/beanstalkd,lzpfmh/beanstalkd,davies/beanstalkd,mickeyouyou/beanstalkd,LomoX-Offical/beanstalkd-win,pinguo-xudianyang/beanstalkd,bmhatfield/beanstalkd,wfxiang08/beanstalkd,orangeholic/beanstalkd,tdg5/beanstalkd,kr/beanstalkd,tdg5/beanstalkd,lzpfmh/beanstalkd,qbdsoft/beanstalkd,justintung/beanstalkd,aidaima/beanstalkd,handautsav/beanstalkd,CompendiumSoftware/beanstalkd,diditaxi/beanstalkd,JensRantil/beanstalkd,Qihoo360/beanstalkd-win,qbdsoft/beanstalkd,Qihoo360/beanstalkd-win,potatosalad/beanstalkd,cgvarela/beanstalkd,naderman/beanstalkd,LomoX-Offical/beanstalkd-win,bmhatfield/beanstalkd,JensRantil/beanstalkd,naderman/beanstalkd,r3jack/beanstalkd,PhillipMwaniki/beanstalkd,yetone/beanstalkd,amyvmiwei/beanstalkd,mobliyishengyuan/beanstalkd,r3jack/beanstalkd,wyzssw/beanstalkd,ifduyue/beanstalkd,mobliyishengyuan/beanstalkd,aidaima/beanstalkd,wyzssw/beanstalkd,handautsav/beanstalkd,kr/beanstalkd,pinguo-xudianyang/beanstalkd,justintung/beanstalkd,cgvarela/beanstalkd,naderman/beanstalkd,yetone/beanstalkd,diditaxi/beanstalkd,ifduyue/beanstalkd,CompendiumSoftware/beanstalkd,mickeyouyou/beanstalkd,amyvmiwei/beanstalkd,PhillipMwaniki/beanstalkd,davies/beanstalkd,wfxiang08/beanstalkd