response 400 on a build means parameters were missing

The request/response look like:

    [INFO] PUT /job/Test%20Job/build
    HTTP Code: 400
    Response Body: <html><head><title>Error 400</title></head><body bgcolor="#ffffff"><h1>Status Code: 400</h1>Exception: Nothing is submitted<br>Stacktrace: <pre>(none)
Merge pull request #70 from drnic/nothing_submitted

response 400 on a build means parameters were missing