Still trying to track outgoing messages

* lisp/gnorb-gnus.el (gnorb-gnus-check-outgoing-headers): Instead of
  relying on blanking out `gnorb-gnus-sending-message-info' when we're
  done with it, just blank it out before we use it.
(gnorb-gnus-outgoing-make-todo-1): Don't set it to nil

* lisp/gnorb-org.el (gnorb-org-add-id-hash-entry): If we're in capture,
  we need the base buffer.