Bug 139986 [CommonNavigator] Convert catch(Error/Throwable) to SafeRunner
In several places the CN framework uses catch(Error/Throwable) to ensure that code does not bring the framework down. Change these to use SafeRunner.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
*            The element to use in the query
	 * @param considerOverrides
	 * 
	 * @return The set of {@link INavigatorContentDescriptor}s that are
	 *         <i>visible</i> and <i>active</i> for this content service and
	 *         have a <b>triggerPoints</b> expression that is <i>enabled</i> for
	 *         the given element.
	 */
	public Set findDescriptorsByTriggerPoint(Object anElement, boolean considerOverrides) {
		
		
		NavigatorContentDescriptor descriptor = getSourceOfContribution(anElement);
		Set result = new TreeSet(ExtensionSequenceNumberComparator.INSTANCE);
		if (descriptor != null) {
			result.add(descriptor);
		}
		result.addAll(CONTENT_DESCRIPTOR_REGISTRY
				.findDescriptorsForTriggerPoint(anElement, assistant, considerOverrides));
		return result;
	}
	/**
	 * Search for extensions that declare the given element in their
	 * <b>possibleChildren</b> expression.
	 * 
	 * @param anElement
	 *            The element to use in the query
	 * @return The set of {@link INavigatorContentDescriptor}s that are
	 *         <i>visible</i> and <i>active</i> for this content service and
	 *         have a <b>possibleChildren</b> expression that is <i>enabled</i>
	 *         for the given element.