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/StructuredViewer.java
* List of post selection listeners (element type: <code>ISelectionActivateListener</code>).
	 * @see #firePostSelectionChanged
	 */
	private ListenerList postSelectionChangedListeners = new ListenerList(1);	
	
/**
 * Creates a structured element viewer. The viewer has no input, 
 * no content provider, a default label provider, no sorter, and no filters.
 */
protected StructuredViewer() {
}
/**
 * Adds a listener for double-clicks in this viewer.
 * Has no effect if an identical listener is already registered.
 *
 * @param listener a double-click listener
 */
public void addDoubleClickListener(IDoubleClickListener listener) {
	doubleClickListeners.add(listener);
}
/**
 * Adds a listener for selection-open in this viewer.
 * Has no effect if an identical listener is already registered.
 *
 * @param listener a double-click listener
 */
public void addOpenListener(IOpenListener listener) {
	openListeners.add(listener);
}
/**