Fix Error When File Attribute Value is Object

Fix error when `$value = $vo->getValue('displaySanitized');` returns
an object with is not displayable as a string

- Add check is `$text` is object and then if so, if said object has
  a `__toString()` method.
- Replace with 'No Display' string if attribute is object and object
  can not be displayed as string

attributevalueobject, file manager, tostring, displaySanitized