Estou com esse erro e não consigo resolver (Trying to access array offset on null)

Mesmo tipando os valores é retornado esse erro! estou usando o 8.3.9 (cli)

Mail::to($request->user())->send(new SeriesCreated(
            (string) $serie->nome,
            (int) $serie->id,
            (int) $request->seasonsQty,
            (int) $request->episodesPerSeason,
        ));

<?php

namespace App\Mail;

use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Mail\Mailable;
use Illuminate\Mail\Mailables\Content;
use Illuminate\Mail\Mailables\Envelope;
use Illuminate\Queue\SerializesModels;

class SeriesCreated extends Mailable
{
    use Queueable, SerializesModels;

    /**
     * Create a new message instance.
     *
     * @return void
     */
    public function __construct(
        public string $nomeSerie,
        public int $idserie,
        public int $qtdTemporadas,
        public int $episodioPorTemporadas
    ) {}

    /**
     * build the message.
     *
     * @return $this
     */
    public function build()
    {
        return $this->markdown('mail.series-created');
    }

    /**
     * Get the message envelope.
     *
     * @return \Illuminate\Mail\Mailables\Envelope
     */
    public function envelope()
    {
        return new Envelope(
            subject: 'Series Created',
        );
    }

    /**
     * Get the message content definition.
     *
     * @return \Illuminate\Mail\Mailables\Content
     */
    // public function content()
    // {
    //     return new Content(
    //         view: 'view.name',
    //     );
    // }

    /**
     * Get the attachments for the message.
     *
     * @return array
     */
    public function attachments()
    {
        return [];
    }
}