check if there is a session before we evaluate code to initialize it.  it is possible, when closing a previous session, that the plugin is created but with the intention of only closing it, so that it can call exit.  add new function bkHelper.hasSessionId that does throw if there is no session.
Merge pull request #445 from twosigma/namespace-fix

check if there is a session before we evaluate code to initialize it.  i...