RadGridView - You cannot select cells only from Pinned Columns if under them there is unpinned one.

Steps to reproduce:
1. Set SelectionMode property of RadGridView to GridViewSelectionMode.CellSelect.
2. Create 3 left pinned columns
3. Create several unpinned columns.
4. Scroll horizontal scroll bar to hide several unpinned columns under the pinned.
5. Try to select only pinned cells with the selection rectangle.