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
Widget[] widgets = internalFindItems(parentElementOrTreePath);
        
        if (widgets.length == 0) {
			return;
		}
		for (int i = 0; i < widgets.length; i++) {
			internalAdd(widgets[i], parentElementOrTreePath, childElements);
		}        
    }
    /**
     * Find the items for the given element of tree path
     * @param parentElementOrTreePath the element or tree path
     * @return the items for that element
     */
	private Widget[] internalFindItems(Object parentElementOrTreePath) {
		Widget[] widgets = findItems(parentElementOrTreePath);
        if (parentElementOrTreePath instanceof TreePath) {
			TreePath path = (TreePath) parentElementOrTreePath;
			Widget w = internalFindItem(path);
			if (w == null) {
				widgets = new Widget[] { };
			} else {
				widgets = new Widget[] { w };
			}
		} else {
			widgets = findItems(parentElementOrTreePath);
		}
		return widgets;
	}
	/**