Active split reported incorrectly from puppet to 3D view on mouse hover

When hovering mouse over inactive split in e.g. "Quad" split mode in 3D view, the active split in 3D view goes out of sync of what split is highlighted. This can be seen e.g. in camera state toolbar button changing incorrectly when hovering over non-active split. Also e.g. wireframe toggle affects wrong split when active split goes out of sync.

To repro:

• Set "Quad" split mode on 3D view
• Select lower right split as active
• Note camera toggle button state (should be orthographic)
• Slowly move mouse to different split without clicking

--> Camera toggle button changes state. If it is clicked, camera change in non-highlighted split.

This is caused by mouse cursor messaging when hovering over splitter.