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/CheckboxTreeViewer.java
* Gathers the grayed states of the given widget and its
 * descendents, following a pre-order traversal of the tree.
 *
 * @param result a writeable list of elements (element type: <code>Object</code>)
 * @param widget the widget
 */
private void internalCollectGrayed(List result, Widget widget) {
	Item[] items = getChildren(widget);
	for (int i = 0; i < items.length; i++) {
		Item item = items[i];
		if (item instanceof TreeItem && ((TreeItem) item).getGrayed()) {
			Object data = item.getData();
			if (data != null)
				result.add(data);
		}
		internalCollectGrayed(result, item);
	}
}
/**
 * Sets the checked state of all items to correspond to the given set of checked elements.
 *
 * @param checkedElements the set (element type: <code>Object</code>) of elements which are checked
 * @param widget the widget
 */
private void internalSetChecked(Set checkedElements, Widget widget) {
	Item[] items = getChildren(widget);
	for (int i = 0; i < items.length; i++) {
		TreeItem item = (TreeItem) items[i];
		Object data = item.getData();
		if (data != null) {