Select the Clean theme. If docking is available and enabled in Clean's 'config.php' file, then set to 'false' to disable it. Create a course and add a Book with two chapters, a Lesson with two contents pages and a Quiz with two questions. Navigate to the Book and turn on editing under 'Course administration' of the 'Administration' block. Observe that clicking on a chapter link on the 'Table of contents' fake block first causes the content area to shrink and an empty area appear on the right (LTR language) for the 'side-post' DND area. Navigate to the Lesson and observe that clicking on the content page links on the 'Lesson menu' fake block first causes the content area to shrink and an empty area appear on the right (LTR language) for the 'side-post' DND area. Navigate to the Quiz, preview, and observe that clicking on the question number links on the 'Quiz navigation' fake block first causes the content area to shrink and an empty area appear on the right (LTR language) for the 'side-post' DND area. Apply the patch. Repeat clicking of links on the 'Table of contents' for the Book, 'Lesson menu' for the Lesson and 'Quiz navigation' for Quiz does not cause the side-post drop area to appear.