Bug 92988 [Viewers] potential NPE in AbstractTreeViewer
I0426, found with FindBugs 1. AbstractTreeViewer line 832 invokes "siblings.length", but the "if" statement above implies that siblings could be null here. 2. StringFieldEditor line 187 does an unnecessary null check since Text.getText() never returns null (FindBugs was using this to point to line 190 as a potential NPE).
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* Removes all items from the given control.
     * 
     * @param control
     *           the control
     */
    protected abstract void removeAll(Control control);
    /**
     * Removes a listener for expand and collapse events in this viewer. Has no
     * affect if an identical listener is not registered.
     * 
     * @param listener
     *           a tree viewer listener
     */
    public void removeTreeListener(ITreeViewerListener listener) {
        treeListeners.remove(listener);
    }
    
    public void reveal(Object element) {
        Assert.isNotNull(element);
        Widget w = internalExpand(element, true);
        if (w instanceof Item)
            showItem((Item) w);
    }
    /**
     * Returns the rightmost visible descendent of the given item. Returns the
     * item itself if it has no children.
     * 
     * @param item
     *           the item to compute the descendent of
     * @return the rightmost visible descendent or the item iself if it has no