Bug 165368 [Viewers] TreePath.getParentPath() should return empty path
TreePath.getParentPath() specifies that it returns null for an empty path. However, it also returns null for a one element path. I think it should return the empty path for a one element path, to be consistent with an empty path representing a root element in a tree.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreePath.java
/**
	 * Constant for representing an empty tree path.
	 */
	public static final TreePath EMPTY = new TreePath(new Object[0]);
	
	private Object[] segments;
	private int hash;
	/**
	 * Constructs a path identifying a leaf node in a tree.
	 * 
	 * @param segments
	 *            path of elements to a leaf node in a tree, starting with the
	 *            root element
	 */
	public TreePath(Object[] segments) {
		Assert.isNotNull(segments);
		for (int i = 0; i < segments.length; i++) {
			Assert.isNotNull(segments[i]);
		}