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
Set checkedElements = new HashSet(elements.length*2+1);
	for (int i = 0; i < elements.length; ++i) {
		
		internalExpand(elements[i], false);
		checkedElements.add(elements[i]);
	}
	Control tree = getControl();
	tree.setRedraw(false);
	internalSetChecked(checkedElements, tree);
	tree.setRedraw(true);
}
/**
 * Sets the grayed state for the given element in this viewer.
 *
 * @param element the element
 * @param state <code>true</code> if the item should be grayed,
 *  and <code>false</code> if it should be ungrayed
 * @return <code>true</code> if the gray state could be set, 
 *  and <code>false</code> otherwise
 */
public boolean setGrayed(Object element, boolean state) {
	Widget widget = internalExpand(element, false);
	if (widget instanceof TreeItem) {
		((TreeItem) widget).setGrayed(state);
		return true;
	}
	return false;
}
/**
 * Check and gray the selection rather than calling both