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
contributionMemoryFirstClass.put(element, firstClassSource);
			}
		}
	}
	/**
	 * Forget about the specified element
	 * 
	 * @param element
	 *            The element to forget.
	 */
	public void forgetContribution(Object element) {
		synchronized (this) {
			contributionMemory.remove(element);
			contributionMemoryFirstClass.remove(element);
		}
	}
	/**
	 * @param element
	 * @return the remembered NavigatorContentDescriptor
	 */
	public NavigatorContentDescriptor getContribution(Object element)
	{
		NavigatorContentDescriptor desc;
		synchronized (this) {
			desc = (NavigatorContentDescriptor) contributionMemory.get(element);
		}
		return desc;
	}
	
	/**