crash when close (alias already exists)

[Patrice]

Hi,

Today, when I exit zim, this error message appears.

======= Traceback =======
  File "/usr/lib/python2.7/dist-packages/zim/actions.py", line 149, in do_activate
    self.__get__(instance, instance.__class__)()
  File "/usr/lib/python2.7/dist-packages/zim/actions.py", line 132, in func
    self.func(instance, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/zim/gui/__init__.py", line 1003, in save_copy
    SaveCopyDialog(self).run()
  File "/usr/lib/python2.7/dist-packages/zim/gui/__init__.py", line 2574, in __init__
    self.add_shortcut(ui.notebook, page)
  File "/usr/lib/python2.7/dist-packages/zim/gui/widgets.py", line 3661, in add_shortcut
    self.filechooser.add_shortcut_folder(page.source.dir.path)
GError: Le raccourci file:///home/patrice/Notebooks/Notes existe déjà
===

(the last line is french language. Means : the alias (link) file:///home/patrice/Notebooks/Notes already exists.)

OS : xubuntu 17.04. Zim 0.66

This bug appears only one time, after modify a page, and exit. The next use and exit doesn't cause any crash. (Random crash?)

Best regards.