R1:0d8f4170f4dc

Fix an issue when deleting the entire content of an unsubmitted inline comment

Summary: Ref T12733. In this case, the server returns no new `row`, but we would incorrectly try to bind to one.

Test Plan:
- Created a new comment.
- Edited it.
- Deleted all the text.
- Saved changes.
- Before: Header continues to show phantom "1 Unsubmitted Comment", browser error log reflects one error.
- After: Header reflects comment being deleted, error log is quiet.

Reviewers: chad

Reviewed By: chad…