Bug 15844 [Exception Handling] SelectionChange events and NPE
Build 20020508 Due to new global actions there are now more objects listening to selection changes send out by a JFace viewer. We now had the case that one of the listener generated a NPE. As a result all listeners registered after that one didn't receive the selection change event. StructuredViewers should be more fault tolorant to exceptions when informing listeners.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
*/
public boolean isExpandable(Object element) {
	return ((ITreeContentProvider) getContentProvider()).hasChildren(element);
}
/* (non-Javadoc)
 * Method declared on Viewer.
 */
protected void labelProviderChanged() {
	
	Control tree= getControl();
	tree.setRedraw(false);
	
	internalRefresh(tree, getRoot(), false);
	tree.setRedraw(true);
}
/**
 * Creates a new item.
 *
 * @param parent the parent widget
 * @param style SWT style bits
 * @param index if non-negative, indicates the position to insert the item 
 *    into its parent
 * @return the newly-created item 
 */
protected abstract Item newItem(Widget parent, int style, int index);
/**
 * Removes the given elements from this viewer.
 * The selection is updated if required.
 * <p>
 * This method should be called (by the content provider) when elements