PHP Core Warning – yii\base\ErrorException

$_GET = [
    0 => 'site/news',
    'id' => 2,
    'n_cat_id' => 1,
    'l' => 'lv_LV',
];

$_SESSION = [
    '__flash' => [],
    'history' => [
        '/lv/ipasie-piedavajumi/akcijas-instrumentiem.html',
    ],
    'cart' => [],
];