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
return LOCATION_AFTER;
            }
        }
        return LOCATION_ON;
    }
    /**
     * Returns the target item of the given drop event.
     *
     * @param event the event
     * @return The target of the drop, may be <code>null</code>.
     */
    protected Object determineTarget(DropTargetEvent event) {
        return event.item == null ? null : event.item.getData();
    }
    /* (non-Javadoc)
     * Method declared on DropTargetAdapter.
     * The mouse has moved over the drop target.  If the
     * target item has changed, notify the action and check
     * that it is still enabled.
     */
    private void doDropValidation(DropTargetEvent event) {
    	
    	
    	if (event.detail != DND.DROP_NONE && overrideOperation == -1)
    		lastValidOperation = event.detail;
    	
    	currentOperation = lastValidOperation;
        currentEvent = event;
        overrideOperation = -1;
        if (!validateDrop(currentTarget, currentOperation, event.currentDataType)) {