DockingBarMorph oldKeyboardFocus holds onto garbage

     just had a case where DockingBarMorph oldKeyboardFocus was the only reference to an Inspector on an object.  The Inspector had been closed, and hence the object it was referencing should have been garbage collected except for the reference from oldKeyboardFocus.  Anyone who understands this could want to try and void oldKeyboardFocus when it is referencing a model whose window is closed?