[FIX] ItemLink didn't discriminate between an unset link and an invalid link...
- [FIX] ItemLink didn't discriminate between an unset link and an invalid link...
- [FIX] ItemLink didn't discriminate between an unset link and an invalid link (a link to an item that doesn't or no longer exists). Add a unit test for this condition and some general ItemLink smoke tests.
See merge request !5347 (merged)