ApiBlock returns the following error instead of a proper JSON result when re-blocking a user who isn't already blocked:
"Catchable fatal error: Argument 1 passed to Block::equals() must be an instance of Block, null given, called in /var/www/w24/includes/specials/SpecialBlock.php on line 725 and defined in /var/www/w24/includes/Block.php on line 192"