"CustomNameVisible": Expected a tag of type ByteTag, got StringTag

Assume this is my fault when making a plugin, not the owner of Slapper's fault.
Trying to upgrade from very old-y server and got this error from Slapper entities when constructing:

Code:

[Server thread/CRITICAL]: RuntimeException: "Expected a tag of type pocketmine\nbt\tag\ByteTag, got pocketmine\nbt\tag\StringTag" (EXCEPTION) in "src/pocketmine/nbt/tag/CompoundTag" at line 99
[Server thread/DEBUG]: #0 src/pocketmine/nbt/tag/CompoundTag(175): pocketmine\nbt\tag\CompoundTag->getTag(string CustomNameVisible, string pocketmine\nbt\tag\ByteTag)
[Server thread/DEBUG]: #1 src/pocketmine/nbt/tag/CompoundTag(199): pocketmine\nbt\tag\CompoundTag->getTagValue(string CustomNameVisible, string pocketmine\nbt\tag\ByteTag, integer 1, boolean )
[Server thread/DEBUG]: #2 src/pocketmine/entity/Entity(834): pocketmine\nbt\tag\CompoundTag->getByte(string CustomNameVisible, integer 1)
[Server thread/DEBUG]: #3 src/pocketmine/entity/Living(71): pocketmine\entity\Entity->initEntity()
[Server thread/DEBUG]: #4 src/pocketmine/entity/Entity(539): pocketmine\entity\Living->initEntity()
[Server thread/DEBUG]: #5 src/pocketmine/entity/Entity(256): pocketmine\entity\Entity->__construct(pocketmine\level\Level object, pocketmine\nbt\tag\CompoundTag object)
[Server thread/DEBUG]: #6 src/pocketmine/level/format/Chunk(746): pocketmine\entity\Entity::createEntity(string Zombie, pocketmine\level\Level object, pocketmine\nbt\tag\CompoundTag object)
[Server thread/DEBUG]: #7 src/pocketmine/level/Level(2690): pocketmine\level\format\Chunk->initChunk(pocketmine\level\Level object)
[Server thread/DEBUG]: #8 src/pocketmine/level/Level(2335): pocketmine\level\Level->loadChunk(integer -1, integer 0, boolean 1)
[Server thread/DEBUG]: #9 src/pocketmine/level/Level(2958): pocketmine\level\Level->getChunk(integer -1, integer 0, boolean 1)
[Server thread/DEBUG]: #10 src/pocketmine/Player(969): pocketmine\level\Level->populateChunk(integer -1, integer 0)
[Server thread/DEBUG]: #11 src/pocketmine/Player(1743): pocketmine\Player->sendNextChunk()
[Server thread/DEBUG]: #12 src/pocketmine/Server(2537): pocketmine\Player->checkNetwork()
[Server thread/DEBUG]: #13 src/pocketmine/Server(2274): pocketmine\Server->tick()
[Server thread/DEBUG]: #14 src/pocketmine/Server(2149): pocketmine\Server->tickProcessor()
[Server thread/DEBUG]: #15 src/pocketmine/Server(1737): pocketmine\Server->start()
[Server thread/DEBUG]: #16 src/pocketmine/PocketMine(554): pocketmine\Server->__construct(BaseClassLoader object, pocketmine\utils\MainLogger object, string D:\Files\MCPE\PocketMine-MP\, string D:\Files\MCPE\PocketMine-MP\plugins\)

There is some incompatible going on. I tried this but didn't work:

PHP:

class SlapperHuman extends Human
{

    public function __construct(Level $level, CompoundTag $nbt)
    {
        if(!($nbt->getTag("CustomNameVisible") instanceof ByteTag)) {
            $nbt->setByte("CustomNameVisible", 1, true);
        }
        parent::__construct($level, $nbt);
        ...
}

How can I properly rewrite the nbt of the entity?