NullPointerException when importing json when omitting "duration" field

Steps to reproduce:
1: create a Test issue (example: XRAY-7)
2: POST the following data to the REST API ( /rest/raven
/1.0/import/execution )
{
"tests" : [
{
"testKey" : "XRAY-7",
"start" : "2013-05-03T11:47:35+01:00",
"finish" : "2013-05-03T11:50:56+01:00",
"comment" : "test execution test",
"status" : "FAIL",
"results": [

{ "name": "some log", "log": "some log information", "status": "????" }

]
}
]
}
Issue is isolated to the "results" field. Removing the "results" field causes the POST to complete successfully.

Full text from log:
curl -H "Content-Type: application/json" -X POST -u user:password --data @testdata.json http://jira-url/rest/raven/1.0/import/execution