Prevent AssertionError when route has no node parameter in PublishContentLocalTask

When using the Publish Content module alongside the Moderation Sidebar module, clicking the moderation sidebar button on a node page triggers a fatal 500/AJAX error.

This happens because the moderation sidebar renders the local tasks in an off-canvas dialog under its own route:
`/moderation-sidebar/{entity_type}/{entity}/latest`

On this route, the path parameter is named `{entity}` instead of `{node}`. When the local task manager builds the tasks, `PublishContentLocalTask::getTitle()` executes and attempts to load the node using:

$node = $this->nodeStorage->load($this->routeMatch->getRawParameter('node'));

Steps to reproduce

1. Enable the publishcontent and moderation_sidebar modules.
2. View a moderated node page and click the "Moderation Sidebar" tab/button.
3. The sidebar AJAX request fails with a 500 error due to the AssertionError.