Quand aucune date de fin n'es spécifiée il assume qu'il y en a une dans son test de formulaire, ce qui provoque des erreurs 500

https://ae2.utbm.fr/equipe_info/sith/issues/115/

KeyError: 'end_date'
(8 additional frame(s) were not displayed)
...
  File "django/forms/forms.py", line 183, in is_valid
    return self.is_bound and not self.errors
  File "django/forms/forms.py", line 175, in errors
    self.full_clean()
  File "django/forms/forms.py", line 385, in full_clean
    self._clean_form()
  File "django/forms/forms.py", line 412, in _clean_form
    cleaned_data = self.clean()
  File "com/views.py", line 241, in clean
    if self.cleaned_data["start_date"] > self.cleaned_data["end_date"]: