Map is not printed correctly to stdout when HTTP Referer is empty.

[ruedigergad]

Sample output showing the issue:
{"PcapHeader" {"timestampInNanos" 1345332080314336000, "wirelen" 574},
"DataLinkLayer"
{"index" 0,
"destination" "00:04:0E:3D:B0:86",
"source" "74:DE:2B:08:78:09",
"next" 2},
"NetworkLayer"
{"index" 1,
"destination" "62.146.26.38",
"source" "192.168.0.198",
"id" 39943,
"tos" 0,
"ttl" 64,
"next" 4},
"Tcp"
{"index" 2,
"destination" 80,
"source" 58118,
"ack" 87565262,
"seq" 2360074209,
"flags" #{"PSH" "ACK"},
"next" 13},
"Http"
{"index" 3,
"RequestUrl" "/css/top.b64-DtuWNk.css",
"Referer"
"RequestMethod" "GET",
"RequestVersion" "HTTP/1.1"}}