Steps to reproduce:

1. Create a project
2. Add View3D
3. Select the directional light by clicking it in the 3D Editor
4. Move the light on all axes a bit by grabbing the move handle in the center of the gizmo (the grey sphere)
5. Click somewhere else in the scene
6. -> rectangle around the light icon is visible as though mouse was hovered over it

Sometimes this happens also when using the other handles, but not always.