Empty file reference field causes a warning to occur

When indexing, in the event that an entity contains a field but that field does not contain a value it still proceeds and tries to foreach through that array (which wouldn't be an array) and therefore you receive the following error:

Invalid argument supplied for foreach() callback_attachments_references_settings.inc:38

My proposed solution would be to check if the referenced entities is empty, and continue with the next field if it is.

// Manage case of field having no value and continue with next field.
if (empty($referenced_entities)) {
  continue;
}