Php 无额外字段的Laravel同步

我正在try 将一个简单的belongsToMany关系保存到我的数据库中.首先，我的桌子:

    Schema::create('user_activity_log', function (Blueprint $table) {
        $table->unsignedBigInteger('activity_id');
        $table->unsignedBigInteger('log_id');
        $table->unsignedInteger('sets');
        $table->unsignedInteger('reps');
        $table->primary(['activity_id', 'log_id']);

        $table->foreign('activity_id')->references('id')->on('user_activities')
            ->onDelete('cascade')
            ->onUpdate('cascade');

        $table->foreign('log_id')->references('id')->on('user_logs')
            ->onDelete('cascade')
            ->onUpdate('cascade');
    });

我的Log和Activity型号有这样的关系:

日志(log):

public function activities()
{
    return $this->belongsToMany(练习::class, 'user_activity_log', 'log_id', 'activity_id')->withPivot(['sets', 'reps']);
}

练习:

public function logs()
{
    return $this->belongsToMany(日志(log)::class, 'user_activity_log', 'activity_id', 'log_id')->withPivot(['sets', 'reps']);
}

在向现有日志(log)添加新活动时，在我的存储方法中，我只需执行以下操作:

$log->activities()->syncWithoutDetaching([
    $request->input('activity_id') => [
        'sets' => $request->input('sets'),
        'reps' => $request->input('reps')
    ]
]);

我收到以下错误:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'id' in 'where clause' 

select * from `user_activity_log` where `id` = 0 limit 1

不过，数据正在保存，所以当我刷新页面并再次提交表单时，没有任何错误.我不明白为什么它要在user_activity_log表中找到id.