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
* <p>
 * This method is internal to the framework; subclassers should not call
 * this method.
 * </p>
 *
 * @param element the element
 */
protected void unmapElement(Object element) {
	if (elementMap != null) {
		elementMap.remove(element);
	}
}
/**
 * Removes the given association from the internal element to widget map.
 * Does nothing if mapping is disabled, or if the given element does not map
 * to the given item.
 * <p>
 * This method is internal to the framework; subclassers should not call
 * this method.
 * </p>
 *
 * @param element the element
 * @since 2.0
 */
protected void unmapElement(Object element, Widget item) {
	
	if (elementMap != null && elementMap.get(element) == item) {
		
		unmapElement(element);
	}