Deleting a note after editing another results in a Javascript error

1. Go to an Issuable with at least two notes.
2. Edit one note and submit the change.
3. Delete a note other than the one you edited.

Result: The note is deleted on the backend but doesn't disappear from the page immediately. JavaScript console shows: Uncaught TypeError: Cannot read property 'lastChild' of undefined

cc @jschatz1