SSU2: Fix uncaught IAE caused by itags with zero values (Gitlab #415)
We were passing null to DatagramPacket.setSocketAddress(), caused by confusion with whether the RouterAddress was direct or indirect. It had introducers but itag0-2 were all zeros, so UDPAddress.getIntroducerCount() returned zero. These addresses were created by i2pd, their bug fixed in 2.49.0/0.9.60. Fixed in the OutboundEstablishState2 constructor, throwing IAE there, and catching in EstablishmentManager to prevent the attempted connection.
Closes #415 (closed)