Problem description: The positioning of the debug area is not fixed on a full dashboard in edit mode - if you scroll down to the very end of the dashboard without focusing on the last widgets and then will hover over one of the last widgets, then the debug area will be shifted to a pseudo random position below the cursor.
In such cases the debug area should either be shifted by the size of the "Add widget" placeholder or not shifted at all (since the dashboard is already full).

Steps to reproduce:

1. Create a dashboard that is completely full with widgets
2. Add Admin used to the "Enabled debug mode" user group
3. Enable debug mode
4. Open the previously created dashboard in edit mode
5. Scroll down to the very end of the dashboard without hovering over the widgets
6. Once the bottom is reached - hover over one of the widgets in the last row of the dashboard.

Result: the Debug area is being shifted down by some non-logical amount of space
Expected: the Debug area should either be shifted by the size of the "Add widget" placeholder, of not shifted at all, since the dashboard is already full

Example: