Ajout d'un cas chaine nulle

src/agenda_culturel/models.py

@@ -35,6 +35,8 @@ logger = logging.getLogger(__name__)
 
 
 def remove_accents(input_str):
+    if input_str is None:
+        return None
     nfkd_form = unicodedata.normalize("NFKD", input_str)
     return "".join([c for c in nfkd_form if not unicodedata.combining(c)])