When checking the list view by category, and if the category is empty or contains passed events, nothing is shown. Normal i guess.
But the message who than appears is illogical.
No matching events listed under %s. Check out upcoming events for this category or view the full calendar.
If $s is the cat name (and it is the cat name), and if nothing is matching, it means probably that the cat doesn't contain something. So why would you want to check for upcoming events in this category (if nothing is matching ?).