why error?

hi everyone please help me
why does plugin error?

Error:Call to a member function setArmorItem() on null[206]

public function onJoin(PlayerJoinEvent $event){
$player = $event->getPlayer();
$name = $player->getName();
$H = $this->h;
$T = $this->t;
if($this->game == false){
$this->players = $this->players + 1;
if($H > $T / 4){
[206]$player->getInventory()->setArmorItem(0,Item::get(298,0,1));
$player->getInventory()->sendArmorContents($player);
$this->t = $T + 1;
$player->setNameTagVisible(false);
$player->removeAllEffects();
}elseif($H < $T){
$player->getInventory()->setArmorItem(0,Item::get(310,0,1));
$player->getInventory()->sendArmorContents($player);
$this->h = $H + 1;
$player->setNameTagVisible(false);
$effect = Effect::getEffect(1);
$effect->setDuration(114514);
$effect->setAmplifier(3);
$effect->setVisible(true);
$player->addEffect($effect);
}elseif($H == $T){
$player->getInventory()->setArmorItem(0,Item::get(298,0,1));
$player->getInventory()->sendArmorContents($player);
$this->t = $T + 1;
$player->removeAllEffects();
return true;
}
}
if($this->game === true){
$player->getInventory()->setArmorItem(0,Item::get(314,0,1));
$player->getInventory()->sendArmorContents($player);
}
}

Please use [ PHP ][/PHP] next time.
I am unsure, as I have never used setArmorItem before (or seen it).
Instead, you should do:

PHP:

$player->getInventory->setItem($slot, Item:get(/*add you item Id here*/);

Eh... One of the code fields are blank. Maybe you should fill it in, instead of giving him the feeling you haven't answered his post completely? Please correct me if I'm wrong.

I am on my iPad. I may have accidentally pressed a wrong button. Thanks for the reminder.

Lol. I always use my iPad and I never make a mistake(totally)!

They meant to do [php][/php]