UPnP: Prevent NPE on socket creation fail (ticket #1681)

router/java/src/org/cybergarage/upnp/ssdp/HTTPUSocket.java

@@ -92,6 +92,9 @@ public class HTTPUSocket
 	{
 		if (0 < localAddr.length())
 			return localAddr;
+		// I2P prevent NPE #1681
+		if (ssdpUniSock == null)
+			return "";
 		return ssdpUniSock.getLocalAddress().getHostAddress();
 	}