Normally, when the review dialog is open, if there are no comments the

footer text field will be hidden. However, it is possible for a user to

create some comments, add a footer, and then delete the comments. When

that user opens the review dialog again, the footer will be hidden and

thus uneditable.
We no longer hide the footer text field when it has text. Additionally,

if while the review dialog is open the footer text is cleared and there

are no open comments, it will be hidden.
A unit test has been added to test this new behaviour and ensure it does

not regress. Other unit tests have been updated to account for this new

behaviour.
Testing done:

- Ran JS tests.

- Created a review with top and bottom text. Clearing the bottom text

  caused the footer text editor to disappear.

Ran JS tests.
Created a review with top and bottom text. Clearing the bottom text

  caused the footer text editor to disappear.