Fix error in SMTP settings when not changing password

src/pretix/base/forms/__init__.py

@@ -113,10 +113,13 @@ class SettingsForm(i18nfield.forms.I18nFormMixin, HierarkeyForm):
             if isinstance(f, (RelativeDateTimeField, RelativeDateField)):
                 f.set_event(self.obj)
 
-    def save(self):
+    def _unmask_secret_fields(self):
         for k, v in self.cleaned_data.items():
             if isinstance(self.fields.get(k), SecretKeySettingsField) and self.cleaned_data.get(k) == SECRET_REDACTED:
                 self.cleaned_data[k] = self.initial[k]
+
+    def save(self):
+        self._unmask_secret_fields()
         return super().save()
 
     def clean(self):

src/pretix/control/views/mailsetup.py

@@ -243,6 +243,8 @@ class MailSettingsSetupView(TemplateView):
                 messages.success(request, _('Your changes have been saved.'))
                 return redirect(self.get_success_url())
             else:
+                self.smtp_form._unmask_secret_fields()
+
                 backend = get_connection(
                     backend=settings.EMAIL_CUSTOM_SMTP_BACKEND,
                     host=self.smtp_form.cleaned_data['smtp_host'],