3447630: Add filename property to the ResultRow.
Closes #3447630
ResultRow object has all the asset information under the asset
key, but when FieldPluginBase.php getValue()
function tries to get the value for the field it cannot find it based on the field name/alias because everything is under the asset
key. It is a quick fix to add the filename there, but it worth considering just reformat the code here like $event->addResult(new ResultRow($asset);
and adjust the code accordingly.