Disable scales if no items are available

ram/portal/templates/cards/scale.html

@@ -28,7 +28,7 @@
               </tbody>
             </table>
             <div class="d-grid gap-2 mb-1 d-md-block">
-              <a class="btn btn-sm btn-outline-primary" href="{% url 'filtered' _filter="scale" search=d.item.slug %}">Show all rolling stock</a>
+              <a class="btn btn-sm btn-outline-primary{% if d.item.num_items == 0 %} disabled{% endif %}" href="{% url 'filtered' _filter="scale" search=d.item.slug %}">Show all rolling stock</a>
               {% if request.user.is_staff %}<a class="btn btn-sm btn-outline-danger" href="{% url 'admin:metadata_scale_change' d.item.pk %}">Edit</a>{% endif %}
             </div>
           </div>

ram/portal/views.py

@@ -7,7 +7,7 @@ from urllib.parse import unquote
 from django.views import View
 from django.http import Http404, HttpResponseBadRequest
 from django.db.utils import OperationalError, ProgrammingError
-from django.db.models import Q
+from django.db.models import Q, Count
 from django.shortcuts import render, get_object_or_404, get_list_or_404
 from django.core.exceptions import ObjectDoesNotExist
 from django.core.paginator import Paginator
@@ -507,7 +507,9 @@ class Scales(GetData):
     queryset = Scale.objects.all()
 
     def get_data(self, request):
-        return Scale.objects.all()
+        return Scale.objects.annotate(
+            num_items=Count("rollingstock")
+        )  # .filter(num_items__gt=0) to filter data with no items
 
 
 class Types(GetData):