* NTCP: Hopefully prevent this:

   java.lang.IllegalStateException: Unable to serialize the message (net.i2p.data.i2np.DatabaseStoreMessage): Invalid key type
	at net.i2p.data.i2np.I2NPMessageImpl.toByteArray(I2NPMessageImpl.java:238)
	at net.i2p.router.transport.ntcp.NTCPConnection.bufferedPrepare(NTCPConnection.java:668)
	at net.i2p.router.transport.ntcp.NTCPConnection.send(NTCPConnection.java:295)
	at net.i2p.router.transport.ntcp.NTCPConnection.enqueueFloodfillMessage(NTCPConnection.java:412)
	at net.i2p.router.transport.ntcp.NTCPConnection.enqueueInfoMessage(NTCPConnection.java:373)
	at net.i2p.router.transport.ntcp.NTCPTransport.outboundMessageReady(NTCPTransport.java:179)
	at net.i2p.router.transport.TransportImpl.send(TransportImpl.java:339)
      ...