Category Automatic Redirect Not Working

I’ve deleted several categories from my blog. Until recently, WordPress would automatically do url “name” redirects, e.g.:

I deleted the online-news category. Therefore, if any, say, Google visitor clicked on the link

https://www.altfg.com/blog/online-news/arn-the-knight-templar-controversy/

once that page was loaded, that link would appear on the url window as:

https://www.altfg.com/blog/european-cinema/arn-the-knight-templar-controversy/

That’s how it should be.

That automatic “category-name redirect” (I’m not sure if this is the right term) is no longer taking place. There’s still a redirect, the page is loaded, but under the old category name:

https://www.altfg.com/blog/online-news/arn-the-knight-templar-controversy/

even though that category no longer exists.

Is there anything I need to do — short of a Redirect 301 for each post , as that would be too time-consuming — to make WordPress automatically do what it had been doing previously?

I’m not sure if the automatic category-name update in the url window stopped working after I upgraded to 2.6 (from 2.5.2 or .3), but it may have been so.

Any assistance would be much appreciated.

Andre