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/extensions/NavigatorContentDescriptorManager.java
isOverridden = addDescriptorsConsideringOverrides(anElement, descriptor.getOverriddingExtensions(),
						aVisibilityAssistant, overridingDescriptors, possibleChild);
				if (!isOverridden && isApplicable) {
					theFoundDescriptors.add(descriptor);
				} else if (isOverridden) {
					theFoundDescriptors.addAll(overridingDescriptors);
				}
			} else if (isApplicable) {
				theFoundDescriptors.add(descriptor);
			}
		}
		return initialSize < theFoundDescriptors.size();
	}
	/**
	 * Returns the navigator content descriptor with the given id.
	 * 
	 * @param id
	 *            The id of the content descriptor that should be returned
	 * @return The content descriptor of the given id
	 */
	public NavigatorContentDescriptor getContentDescriptor(String id) {
		return (NavigatorContentDescriptor) allDescriptors.get(id);
	}
	/**
	 * 
	 * @param descriptorId
	 *            The unique id of a particular descriptor
	 * @return The name (value of the 'name' attribute) of the given descriptor
	 */
	public String getText(String descriptorId) {