[grooveshark] fix bug when Year field is empty in grooveshark json
[grooveshark] fix bug when Year field is empty in grooveshark json

laurent-george/weboob,laurent-george/weboob,RouxRC/weboob,nojhan/weboob-devel,Konubinix/weboob,willprice/weboob,sputnick-dev/weboob,willprice/weboob,frankrousseau/weboob,Konubinix/weboob,Konubinix/weboob,laurent-george/weboob,willprice/weboob,nojhan/weboob-devel,frankrousseau/weboob,nojhan/weboob-devel,sputnick-dev/weboob,frankrousseau/weboob,sputnick-dev/weboob,RouxRC/weboob,RouxRC/weboob