Useful error message for wrong topic modes

modules/admin.py

@@ -171,7 +171,8 @@ def topic_new():
     if event_id is None:
         return redirect(url_for(".index"))
     form.event_id.data = event_id
-    return render_layout("admin_topic_new.html", form=form)
+    event = Event.query.filter_by(id=event_id).first()
+    return render_layout("admin_topic_new.html", form=form, event=event)
 
 @admin.route("/topic/delete")
 @login_required

templates/admin_topic_new.html

@@ -3,5 +3,5 @@
 {% block title %}Add Topic - Administration{% endblock %}
 
 {% block content %}
-        {{ render_form(form, action_url=url_for(".topic_new", id=id), action_text="Add", title="Create Topic") }}
+        {{ render_form(form, action_url=url_for(".topic_new", id=id, event_id=event.id), action_text="Add", title="Create Topic") }}
 {% endblock %}