When running `arc diff --preview`, visiting the diff URL produces the following error:
Unhandled Exception ("PhabricatorDataNotAttachedException")
Attempting to access attached data on DifferentialDiff (via getBuildable()), but the data is not actually attached. Before accessing attachable data on an object, you must load and attach it.
Data is normally attached by calling the corresponding needX() method on the Query class when the object is loaded. You can also call the corresponding attachX() method explicitly.
{F702537}