Empty tag is removed when it's the only element in the content

[Jamie]

Steps to reproduce

1. Insert <div id="foo">&nbsp;</div> in the Source view
2. Switch out of source view and back in
3. <div> is removed

Expected result

Div should remain. If you add <p>&nbsp;</p> before or after the div remains.

Actual result

Div is removed.

Other details (browser, OS, CKEditor version, installed plugins)

Chrome 58.0.3029.81, Win 10, CKEditor 4.6.2

Config has:

config.protectedSource.push(/<i[^>]*><\/i>/g);

This prevents <i> from being removed, but:

config.protectedSource.push(/<div[^>]*><\/div>/g);

In the scenario above makes no difference to <div> being removed.

Added text to the div i.e. <div id="foo">Test</div> stops it from being removed.

[Jamie]

Adding a comment tag before or after the div also prevents it from being removed:

<!-- Begin Snippet -->
<div id="foo">&nbsp;</div>