Bug 221768 [Viewers] Fix for bug 210747 causes NPE when parent is TreePath.EMPTY
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* appear as children of the given parent.
	 *
	 * @param parent the parent element
	 * @param elements
	 *            the elements to remove
	 * @since 3.1
	 */
	protected void internalRemove(Object parent, Object[] elements) {
		CustomHashtable toRemove = new CustomHashtable(getComparer());
		for (int i = 0; i < elements.length; i++) {
			toRemove.put(elements[i], elements[i]);
		}
		
		Widget[] parentItemArray = findItems(parent);
		for (int i = 0; i < parentItemArray.length; i++) {
			Widget parentItem = parentItemArray[i];
			
			Item[] children = getChildren(parentItem);
			for (int j = 0; j < children.length; j++) {
				Item child = children[j];
				Object data = child.getData();
				if (data != null && toRemove.containsKey(data)) {
					disassociate(child);
					child.dispose();
				}
			}
		}
	}
	/**
	 * Sets the expanded state of all items to correspond to the given set of