Bug 130976 [Viewers] Error is calculation of parent path when calling TreePathViewerSorter
There is an error in the parent path calculation in AbstractTreeViewer#getSortedChildren. If the input of the viewer is passed, a tee path of length one is passed to the sorter but a null should be passed (as mentioned in the method spec). I will attach a patch.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
*           subtrees are ignored
     * @return the next item, or <code>null</code> if none
     */
    protected Item getNextItem(Item item, boolean includeChildren) {
        if (item == null) {
            return null;
        }
        if (includeChildren && getExpanded(item)) {
            Item[] children = getItems(item);
            if (children != null && children.length > 0) {
                return children[0];
            }
        }
        
        
        Item parent = getParentItem(item);
        if (parent == null) {
            return null;
        }
        Item[] siblings = getItems(parent);
        if (siblings != null){
        	if(siblings.length <= 1) {
				return getNextItem(parent, false);
			}
        	
        	for (int i = 0; i < siblings.length; i++) {
                if (siblings[i] == item && i < (siblings.length - 1)) {
                    return siblings[i + 1];
                }
            }