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
* @param control
     *           the control
     * @return the number of children
     */
    protected abstract int getItemCount(Control control);
    /**
     * Returns the number of child items of the given SWT item.
     * 
     * @param item
     *           the item
     * @return the number of children
     */
    protected abstract int getItemCount(Item item);
    /**
     * Returns the child items of the given SWT item.
     * 
     * @param item
     *           the item
     * @return the child items
     */
    protected abstract Item[] getItems(Item item);
    /**
     * Returns the item after the given item in the tree, or <code>null</code>
     * if there is no next item.
     * 
     * @param item
     *           the item
     * @param includeChildren
     *           <code>true</code> if the children are considered in
     *           determining which item is next, and <code>false</code> if