Fix: fix validate error by regexp when value is empty
Fix: fix validate error by regexp when value is empty

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