InstanceView: Omit comment if it's empty

test/pleroma/web/mastodon_api/controllers/instance_controller_test.exs

@@ -171,6 +171,22 @@ defmodule Pleroma.Web.MastodonAPI.InstanceControllerTest do
              ] == json_response_and_validate_schema(conn, 200)
     end
 
+    test "omits comment field if comment is empty", %{conn: conn} do
+      clear_config([:mrf_simple, :reject], ["fediverse.pl"])
+
+      conn = get(conn, "/api/v1/instance/domain_blocks")
+
+      assert [
+               %{
+                 "digest" => "55e3f44aefe7eb022d3b1daaf7396cabf7f181bf6093c8ea841e30c9fc7d8226",
+                 "domain" => "fediverse.pl",
+                 "severity" => "suspend"
+               } = domain_block
+             ] = json_response_and_validate_schema(conn, 200)
+
+      refute Map.has_key?(domain_block, "comment")
+    end
+
     test "returns empty array if mrf transparency is disabled", %{conn: conn} do
       clear_config([:mrf, :transparency], false)