List of steps to reproduce (step by step, including full links if applicable):

• Keep open a tab with some Echo buttons.
• Log out for testing purposes (usually this happens automatically, hence why it is important to communicate in message).
• Try to open a notification drawer.
• Read ‘There are no notifications’ message (MediaWiki:Echo-notification-placeholder) instead of something that would indicate that the user has been logged out.

What should have happened instead?:

Echo extension should indicate that the user is logged out if API returns a response indicating that. For Echo notifications, that is currently the case:

{"error":{"code":"login-required","info":"You must be logged in.","docref":"See https://ru.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/postorius/lists/mediawiki-api-announce.lists.wikimedia.org/> for notice of API deprecations and breaking changes."},"servedby":"mw1388"}

The error should be caught and displayed to user, so they would not be mistaken that they don’t have or have lost all their notifications somehow.

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc:
Any