allow empty string for version and user_agent
allow empty string for version and user_agent

ayeowch/bitnodes,NiKiZe/bitnodes,Pan0ram1x/bitnodes,NiKiZe/bitnodes,ayeowch/bitnodes,jmaurice/bitnodes,reddcoin-project/reddnodes,Pan0ram1x/bitnodes,jmaurice/bitnodes,reddcoin-project/reddnodes