Bug 232777 [Viewers] ViewerDropAdapter holds currentTarget forever
Build ID: 3.3.2 Member currentTarget should be set to null after drop or after cancel, because it holds a domain object, which can't be garbage collected after Viewer.setInput(null).
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ViewerDropAdapter.java
currentOperation = DND.DROP_NONE;
        }
        
        if (overrideOperation != -1)
        	event.detail = overrideOperation;
        else
        	event.detail = currentOperation;
        currentEvent = null;
    }
    /* (non-Javadoc)
     * Method declared on DropTargetAdapter.
     * The drag has entered this widget's region.  See
     * if the drop should be allowed.
     */
    public void dragEnter(DropTargetEvent event) {
        currentTarget = determineTarget(event);
        doDropValidation(event);
    }
    /* (non-Javadoc)
     * Method declared on DropTargetAdapter.
     * The drop operation has changed, see if the action
     * should still be enabled.
     */
    public void dragOperationChanged(DropTargetEvent event) {
        currentTarget = determineTarget(event);
        doDropValidation(event);
    }
    /* (non-Javadoc)
     * Method declared on DropTargetAdapter.
     * The mouse has moved over the drop target.  If the