fix paranllelLimit memory leak when use single data
fix paranllelLimit memory leak when use single data

maxzhang/thinkjs,snadn/thinkjs,75team/thinkjs,thinkjs/thinkjs,akira-cn/thinkjs,akira-cn/thinkjs,akira-cn/thinkjs,75team/thinkjs,maxzhang/thinkjs,75team/thinkjs,maxzhang/thinkjs,Qihoo360/thinkjs