don’t pass version negotiation packets to the session

Version negotiation packets don’t have any payload. They must not be
passed to the session, because they’ll end up there as undecryptable
packets.

client.go

@@ -168,10 +168,8 @@ func (c *client) handlePacket(remoteAddr net.Addr, packet []byte) error {
 	}
 
 	if hdr.VersionFlag {
-		err = c.handlePacketWithVersionFlag(hdr)
-		if err != nil {
-			return err
-		}
+		// version negotiation packets have no payload
+		return c.handlePacketWithVersionFlag(hdr)
 	}
 
 	c.session.handlePacket(&receivedPacket{
@@ -215,7 +213,7 @@ func (c *client) handlePacketWithVersionFlag(hdr *PublicHeader) error {
 		go c.config.ConnState(c.session, ConnStateVersionNegotiated)
 	}
 
-	return nil // version negotiation packets have no payload
+	return nil
 }
 
 func (c *client) cryptoChangeCallback(_ Session, isForwardSecure bool) {