comments: fix exception with group_by=comment param.

app/views/comments/partials/show/_comment.html.erb

@@ -12,7 +12,7 @@
            data-is-deleted="<%= comment.is_deleted? %>"
            data-is-sticky="<%= comment.is_sticky? %>"
            data-below-threshold="<%= comment.score < CurrentUser.user.comment_threshold %>"
-           <% if policy(moderation_reports).show? %>
+           <% if moderation_reports.present? && policy(moderation_reports).show? %>
             data-is-reported="<%= moderation_reports.pluck(:model_id).include?(comment.id) %>"
            <% end %>
            data-is-voted="<%= comment.voted_by?(CurrentUser.user) %>">

test/functional/comments_controller_test.rb

@@ -20,6 +20,7 @@ class CommentsControllerTest < ActionDispatch::IntegrationTest
     context "index action" do
       context "grouped by post" do
         should "render all comments for .js" do
+          @comment = as(@user) { create(:comment, post: @post) }
           get comments_path(post_id: @post.id), xhr: true
 
           assert_response :success
@@ -87,6 +88,7 @@ class CommentsControllerTest < ActionDispatch::IntegrationTest
       end
 
       should "render by comment" do
+        @comment = as(@user) { create(:comment, post: @post) }
         get comments_path(group_by: "comment")
         assert_response :success
       end