I was able to replicate this bug, I've added it to our list.

This has been fixed and will be in the next minor release. The minor is getting pretty hefty with fixes, it will be a nice update once it's released.

I also noticed that if you delete an IP in the Bypass Gateways tab, then immediately click on the Spam Checks tab (without clicking Save), it says: No items to show in this list instead of displaying all the RBLs. This might be resolved with your fix above.