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
this.segments = segments;
	}
	/**
	 * Returns the element at the specified index in this path.
	 * 
	 * @param index
	 *            index of element to return
	 * @return element at the specified index
	 */
	public Object getSegment(int index) {
		return segments[index];
	}
	/**
	 * Returns the number of elements in this path.
	 * 
	 * @return the number of elements in this path
	 */
	public int getSegmentCount() {
		return segments.length;
	}
	/**
	 * Returns the first element in this path.
	 * 
	 * @return the first element in this path
	 */
	public Object getFirstSegment() {
		if (segments.length == 0) {
			return null;
		}
		return segments[0];