[FIX] fix swiss localization for iban not required.

IBAN number not required so it should not be checked if not provided.

easy_my_coop_website/controllers/main.py

@@ -329,6 +329,7 @@ class WebsiteSubscription(http.Controller):
                 return request.render(redirect, values)
 
         iban = kwargs.get("iban")
+        if iban.strip():
             valid = sub_req_obj.check_iban(iban)
 
             if not valid: