New widget placeholder disappears in dashboard edit mode, if too less widgets added

Steps to reproduce:

1. Create new dashboard.
2. Create new small-sized widget on top of the dashboard.
3. Save the dashboard.
4. Click Edit dashboard.
5. Slowly move the mouse cursor over empty area of the dashboard from top to bottom (not touching the created widget).

Result:

As soon as area below the created widget is reached, the new widget placeholder disappears. Then, moving mouse up and down re-enables the new widget placeholder.

Expected:

Placeholder should allow creating widgets at any visible place of the dashboard.