下面的代码片段是收集和显示几个视频的次数。但它显示以下错误：
尝试在null上读取属性“episode”
从这一行：

$course->time = $this->getCourseTime($course->episode->pluck('time'));

AdminController：

public function setCourseTime($episode)
{
    $course = $episode->course;
    $course->time = $this->getCourseTime($course->episode->pluck('time'));
    $course->save();
}

protected function getCourseTime($times)
{
    $timestamp = Carbon::parse('00:00:00');
    foreach ($times as $row)
    {
        $time = strlen($row) == 5 ? strtotime('00:' . $row) : strtotime($row);
        $timestamp->addSecond($time);
    }

    return $timestamp->format('H:i:s');
}

模型Course.php

public function episode()
{
    return $this->hasMany(Episode::class);
}

模型Episode.php

public function courses()
{
    return $this->belongsTo(Course::class);
}

EpisodeController.php

public function store(EpisodeRequest $request)
{

    $episode = Episode::create($request->all());
    $this->setCourseTime($episode);

    return to_route('episode.index');
}