Fix NPE when deleting work with no parent

We were getting the parent to know where to redirect after deleting. If
there is no parent, we shall just redirect them to the works index screen.
Same as last commit except it compiles now yaay
Merge remote-tracking branch 'origin/master' into hr-delete-work-with-parent
Merge pull request #435 from nla/hr-delete-work-with-parent

Fix NPE when deleting work with no parent