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/NavigatorContentDescriptor.java
* 
	 * @return The value specified by the <i>appearsBefore</i> attribute of the
	 *         &lt;navigatorContent/&gt; element.
	 */
	public String getAppearsBeforeId() {
		return appearsBeforeId;
	}
	public boolean isSortOnly() {
		return sortOnly;
	}
	
	/**
	 * Parses the configuration element.
	 * 
	 * @throws WorkbenchException
	 *             if the configuration element could not be parsed. Reasons
	 *             include:
	 *             <ul>
	 *             <li>A required attribute is missing.</li>
	 *             <li>More elements are define than is allowed.</li>
	 *             </ul>
	 */
	private void init() throws WorkbenchException {
		id = configElement.getAttribute(ATT_ID);
		name = configElement.getAttribute(ATT_NAME);
		String priorityString = configElement.getAttribute(ATT_PRIORITY);
		icon = configElement.getAttribute(ATT_ICON);
		String activeByDefaultString = configElement
				.getAttribute(ATT_ACTIVE_BY_DEFAULT);
		activeByDefault = (activeByDefaultString != null && activeByDefaultString