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/actions/CommonActionProviderDescriptor.java
protected boolean hasOverridingDescriptors() {
		return overridingDescriptors != null
				&& !overridingDescriptors.isEmpty();
	}
	protected Iterator dependentDescriptors() {
		return dependentDescriptors.iterator();
	}
	protected Iterator overridingDescriptors() {
		return overridingDescriptors.iterator();
	}
	/**
	 * @return the id of the contributing plugin
	 */
	public String getPluginId() {
		return pluginId;
	}
	
	public String toString() {
		if (toString == null) {
			toString = "CommonActionProviderDescriptor[definedId=" + getDefinedId() + ", visibilityId=" + getId() + ", dependsOn=" + getDependsOnId() + ", overrides=" + getOverridesId() + "]"; 
		}
		return toString;
	} 
	
	/**
	 * Sorts CommonActionProviderDescriptors by priority, and then by defined id. 
	 * @since 3.2
	 *
	 */
	public static class CommonActionProviderDescriptorCompator implements Comparator {