Editing a course topic's summary, switching Atto to the HTML view, then saving changes without actually making any changes introduces vertical spacing between the topic heading and the topic's activities.

Steps to reproduce issue:
1. Create a course. With the default settings four empty topics are shown.
2. Click Turn editing on for the course page and for Topic 1 click Edit, then Edit topic.
3. In the Summary editor field click Show/hide advanced buttons (by default the first toolbar button, then HTML (by default the last toolbar button on row 2).
4. Click Save changes.

Expected results
No changes to the course page.

Actual results
Increased vertical space has been added under the heading Topic 1.