Preserve whitespace around protectedSource entries

[ximunderscore]

Steps to reproduce

1. (optional) Install e.g. “Show Protected” to see protectedSource elements.
2. Set up your CKEditor with e.g. a PHP protectedSource: [/<\?[\s\S]*?\?>/g]
3. Open CKEditor and enter source editing mode
4. Input “<p><?php print_something(); ?> was printed</p>”
5. Exit source editing mode

Expected result

There should be a whitespace between protectedSource block and “was printed”

Actual result

There is no whitespace after the protectedSource block. Re-entering source editing shows that input has changed to “<p><?php print_something(); ?>was printed</p>”.

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

Tested in Chrome 57 and Firefox 52. Using lots of plugins, but this appears to be plugin independent.