Don't allow users without permission to edit the image to see its focal point chooser

wagtail/wagtailimages/views/focal_point_chooser.py

@@ -1,5 +1,6 @@
 from django.shortcuts import get_object_or_404
 from django.contrib.auth.decorators import permission_required
+from django.core.exceptions import PermissionDenied
 
 from wagtail.wagtailadmin.modal_workflow import render_modal_workflow
 from wagtail.wagtailimages.models import get_image_model
@@ -9,6 +10,9 @@ from wagtail.wagtailimages.models import get_image_model
 def chooser(request, image_id):
     image = get_object_or_404(get_image_model(), id=image_id)
 
+    if not image.is_editable_by_user(request.user):
+        raise PermissionDenied
+
     return render_modal_workflow(request, 'wagtailimages/focal_point_chooser/chooser.html', 'wagtailimages/focal_point_chooser/chooser.js', {
         'image': image,
     })