Restore ability to delete bookmark custom title

[diracdeltas]

Fix #7691

Test Plan:

1. automated bookmark tests should pass
2. try editing a bookmark and fully deleting the title. the title field should be empty.

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Test Plan:

[cndouglas]

Now works correctly. Thanks for the quick fix!

[bsclifton]

++ 😄