[FIX] fix mix share if statement

the compare was made between cooperator type and the short name of the
share type. but the cooperator type is the default code and not the
short name which is the displayed label

easy_my_coop/controllers/main.py

@@ -275,7 +275,7 @@ class WebsiteSubscription(http.Controller):
                 max_amount = max_amount - partner.total_value
                 if company.unmix_share_type:
                     share = self.get_selected_share(kwargs)
-                    if partner.cooperator_type != share.short_name:
+                    if partner.cooperator_type != share.default_code:
                         values = self.fill_values(values, is_company, logged)
                         values["error_msg"] = (_("You can't subscribe two "
                                                  "different types of share"))