added new test case in link extractor ('a' tag with no href) and fixed code for correct handling (previous version was raising exception with this case)
added new test case in link extractor ('a' tag with no href) and fixed
code for correct handling (previous version was raising exception with
this case)

pombredanne/portia,naveenvprakash/portia,hanicker/portia,lodow/portia-proxy,sntran/portia,flip111/portia,hmilywb/portia,hmilywb/portia,livepy/portia,livepy/portia,naveenvprakash/portia,chennqqi/portia,NicoloPernigo/portia,Youwotma/portia,NicoloPernigo/portia,amikey/portia,NoisyText/portia,NoisyText/portia,CENDARI/portia,pombredanne/portia,chennqqi/portia,verylasttry/portia,naveenvprakash/portia,Youwotma/portia,sntran/portia,amikey/portia,NicoloPernigo/portia,SouthStar/portia,Suninus/portia,nju520/portia,anjuncc/portia,SouthStar/portia,CENDARI/portia,hanicker/portia,verylasttry/portia,hanicker/portia,PrasannaVenkadesh/portia,livepy/portia,hmilywb/portia,flip111/portia,amikey/portia,asa1253/portia,asa1253/portia,naveenvprakash/portia,sntran/portia,nju520/portia,CENDARI/portia,PrasannaVenkadesh/portia,flip111/portia,pombredanne/portia,hmilywb/portia,Suninus/portia,lodow/portia-proxy,PrasannaVenkadesh/portia,amikey/portia,SouthStar/portia,pombredanne/portia,NoisyText/portia,Suninus/portia,hanicker/portia,anjuncc/portia,NicoloPernigo/portia,nju520/portia,Youwotma/portia,SouthStar/portia,sntran/portia,NoisyText/portia,asa1253/portia,nju520/portia,verylasttry/portia,CENDARI/portia,chennqqi/portia,Youwotma/portia,chennqqi/portia,anjuncc/portia,PrasannaVenkadesh/portia,anjuncc/portia,Suninus/portia,livepy/portia,verylasttry/portia,asa1253/portia,lodow/portia-proxy,flip111/portia