Do not block "add to cart" button when seating is used

src/pretix/presale/templates/pretixpresale/event/index.html

@@ -216,6 +216,7 @@
             <form method="post" data-asynctask
                     data-asynctask-headline="{% trans "We're now trying to reserve this for you!" %}"
                     data-asynctask-text="{% blocktrans with time=event.settings.reservation_time %}Once the items are in your cart, you will have {{ time }} minutes to complete your purchase.{% endblocktrans %}"
+                    class="{% if event.seating_plan_id %}has-seating"{% endif %}
                     action="{% eventurl request.event "presale:event.cart.add" cart_namespace=cart_namespace %}?next={{ cart_redirect|urlencode }}">
                 {% csrf_token %}
                 <input type="hidden" name="subevent" value="{{ subevent.id|default_if_none:"" }}" />

src/pretix/static/pretixpresale/js/ui/main.js

@@ -208,7 +208,7 @@ $(function () {
                 }
             });
         }
-        if (!is_enabled) {
+        if (!is_enabled && !$(".has-seating").length) {
             $("#btn-add-to-cart").prop("disabled", !is_enabled).popover({'content': gettext("Please enter a quantity for one of the ticket types."), 'placement': 'top', 'trigger': 'hover focus'});
         } else {
             $("#btn-add-to-cart").prop("disabled", false).popover("destroy")