Notes plugin should autodetect note taking application

[Nicolas Chachereau]

System: Ubuntu 11.04 Natty Narwhal.
Kupfer package (PPA) version: 0+v206-0ubuntu0~natty~kupferhope
Tomboy package version: 1.6.0-0ubuntu3

Steps to reproduce: Open Kupfer's preferences, make sure the Notes plugin is activated and choose the empty entry in "Work with application". Invoke Kupfer, type a note's name. Once the note is selected, press Enter.

Observed behaviour: nothing happens!
If Kupfer is launched in the terminal, I have following output:

Error [kupfer.plugin.notes]: org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Gnote was not provided by any .service files
Traceback (most recent call last):
  File "/usr/share/kupfer/kupfer/ui/browser.py", line 1563, in _activate
    self.data_controller.activate(ui_ctx=self._make_gui_ctx())
  File "/usr/share/kupfer/kupfer/core/data.py", line 798, in activate
    res, ret = ctx.run(leaf, action, sobject, ui_ctx=ui_ctx)
  File "/usr/share/kupfer/kupfer/core/commandexec.py", line 303, in run
    ret = activate_action(execution_token, obj, action, iobj)
  File "/usr/share/kupfer/kupfer/core/commandexec.py", line 80, in activate_action
    return _activate_action_single(obj, action, iobj, kwargs)
  File "/usr/share/kupfer/kupfer/core/commandexec.py", line 88, in _activate_action_single
    ret = action.activate(obj, **kwargs)
  File "/usr/share/kupfer/kupfer/plugin/notes.py", line 93, in activate
    notes.DisplayNote(noteuri)
AttributeError: 'NoneType' object has no attribute 'DisplayNote'

Clearly, while apparently able to list my notes (or do they come from some sort of cache?), Kupfer then tries to open them with Gnote, and since I'm using Tomboy, it does not work.

I was going to report this bug when I noticed the "Work with application" option. Once correctly set to "Tomboy", things work again. For some reason this option was set to this useless empty entry.

- why is there an empty entry in the first place?
- why can't Kupfer detect I'm using Tomboy? It's the only one installed (e.g. `which gnote' returns 1).

Something in this direction would be nice, to prevent this annoyance