转换集合后，Laravel-Excel导出为空

Question

我的代码目前正在执行成功导出：

$ncrforms = NCRForm::where('created_at', '>=', (new Carbon('first day of last month'))->toDateString())
                        ->where('created_at', '<=', (new Carbon('last day of last month'))->toDateString())
                        ->get();

Excel::create('ncr_forms', function($excel) use($ncrforms) {
    $excel->sheet('Previous Months Forms', function($sheet) use($ncrforms) {
        $sheet->fromArray($ncrforms);
    });
})->export('xls');

这里的问题是，我的收藏中有几列我想要更改，因此我添加了transform()值的步骤：

$ncrforms = NCRForm::where('created_at', '>=', (new Carbon('first day of last month'))->toDateString())
                        ->where('created_at', '<=', (new Carbon('last day of last month'))->toDateString())
                        ->get();

$ncrforms->transform(function($form) {
    $form->responsibility = is_null($form->responsibility) ? $form->responsibility : $form->personResponsible->name;
    $form->user_id = $form->user->name;

    return $form;
});

Excel::create('ncr_forms', function($excel) use($ncrforms) {
    $excel->sheet('Previous Months Forms', function($sheet) use($ncrforms) {
        $sheet->fromArray($ncrforms);
    });
})->export('xls');

但是，新导出现在已经完全没空了 - 电子表格会下载，但不会有任何内容。

我正在使用Laravel-Excel软件包执行导出。

为什么在执行transform()后导出为空 - 在修改我需要的值后，如何在导出不为空之后实现我的目标？