gdpbzr error opening diverged from when there is no parent

I saw the following error when I accidentally tried to open diverged files. I know my branch is the master and without a parent. This same issue can happen to open unpushed files if there is not a push location set. There are two way of dealing with this. The simplest is to catch the NotBranchError error and explain there is no parent or push location. Maybe the menu item could be disabled when the option is not available. I doubt this can be done as the traceback shows, bzrlib assumed the repo was the parent branch so the UI thinks there is parent too.

  File "/home/curtis/.local/share/gedit/plugins/gdp/bzr.py", line 130, in open_changed_files_from_parent
    self.open_changed_files(self._parent_tree)
  File "/home/curtis/.local/share/gedit/plugins/gdp/bzr.py", line 94, in _parent_tree
    self.working_tree.branch.get_parent())
  File "/home/curtis/.local/share/gedit/plugins/gdp/bzr.py", line 82, in _get_branch_revision_tree
    return revision.as_tree(self.working_tree.branch)
  File "/usr/lib/python2.7/dist-packages/bzrlib/revisionspec.py", line 268, in as_tree
    return self._as_tree(context_branch)
...
  File "/usr/lib/python2.7/dist-packages/bzrlib/controldir.py", line 1139, in find_format
    raise errors.NotBranchError(path=transport.base)
bzrlib.errors.NotBranchError: Not a branch: "/home/curtis/Hacking/trunk/".