Do not hide subevent list if filtered list is empty (#6460)

* Do not hide subevent list if filtered list is empty

* Event calendar: Allow to show a message if no events are found

* Apply suggestion from @luelista

Co-authored-by: luelista <weller@rami.io>

* Fix failures on org level

* add aria-hidden if no subevents

* Update src/pretix/base/settings.py

* Update src/pretix/base/settings.py

Co-authored-by: Richard Schreiber <schreiber@pretix.eu>

---------

Co-authored-by: luelista <weller@rami.io>
Co-authored-by: Richard Schreiber <schreiber@rami.io>
Co-authored-by: Richard Schreiber <schreiber@pretix.eu>

src/pretix/base/settings.py

@@ -933,6 +933,23 @@ DEFAULTS = {
                         "is over. You can use it to describe other options to get a ticket, such as a box office.")
         )
     },
+    'event_list_empty_text': {
+        'default': LazyI18nString.from_gettext(
+            gettext_noop('No dates match your criteria.'),
+        ),
+        'type': LazyI18nString,
+        'form_class': I18nFormField,
+        'serializer_class': I18nField,
+        'form_kwargs': dict(
+            label=pgettext_lazy("subevents", "Text for empty date results"),
+            widget=I18nMarkdownTextarea,
+            widget_kwargs={'attrs': {'rows': '2'}},
+            help_text=pgettext_lazy("subevents", "This text will be shown if the calendar or list of dates is empty, "
+                                                 "e.g. because a month does not contain any dates or a filter chosen by the user does "
+                                                 "not find any results. You can use this to advertise ways to get in touch with you to "
+                                                 "arrange further dates. We do not recommend more than one or two sentences.")
+        )
+    },
     'payment_explanation': {
         'default': '',
         'type': LazyI18nString,