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
return getControl();
		}
        return null;
    }
    
    protected Widget doFindItem(Object element) {
        
        Object root = getRoot();
        if (root == null) {
			return null;
		}
        Item[] items = getChildren(getControl());
        if (items != null) {
            for (int i = 0; i < items.length; i++) {
                Widget o = internalFindItem(items[i], element);
                if (o != null) {
					return o;
				}
            }
        }
        return null;
    }
    /**
     * Copies the attributes of the given element into the given SWT item.
     * 
     * @param item
     *           the SWT item
     * @param element
     *           the element
     */