Slot Viewer Revisions: Close when Empty; Undock/Remove slot operations [2]
Bug Number: n/a
Release notes (y/n): No, new development.
For Release Nums: 7.2

When the Slot Viewer becomes empty, i.e. when removing the last slot from the 
Slot Viewer, it should be closed.  That was not happening when DRAGGING the 
last slot off the Slot Viewer.  See change in method:

  SlotQtDlg::slotViewer_detachSlotCol (SlotColRef scRef, QPoint globalPos);

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