Laravel Export: Attempt to read property “second_key” on null

I need to export data with Laravel Export, but the code return ErrorException: Attempt to read property "second_key" on null.

My code:

<?php
namespace AppAdminExtensions;
use EncoreAdminGridExportersExcelExporter;
use MaatwebsiteExcelFacadesExcel;
use MaatwebsiteExcelConcernsFromQuery;
use MaatwebsiteExcelConcernsWithMapping;
use MaatwebsiteExcelConcernsShouldAutoSize;
class DataExporter extends ExcelExporter implements FromQuery, WithMapping, ShouldAutoSize
{
protected $fileName = 'Export Data.xlsx';
    public function headings(): array
    {
        return [
            'ID',
            'Title',
            'Status',
            'Gender',
            'Data',
        ];
    }
    public function map($data): array
    {
        return [
            $data->id,
            $data->title,
            $data->status,
            $data->gender,
            $data->json_data->second_key, // <-- Here's the error
        ];
    }

}

I’ve tried to check using this:

print_r(json_encode($data->json_data));

and this is the result:

{
      "id": 282,
      "second_key": "second_value",
      "third_key": "6200",
      "fourth_key": "0000",
      "fifth_key": 28
}

I’ve also done this:

return [
     $data->id,
     $data->title,
     $data->status,
     $data->gender,
     $data->json_data //Without "second_key"
];

and the excel cell returns the same result:

{
      "id": 282,
      "second_key": "second_value",
      "third_key": "6200",
      "fourth_key": "0000",
      "fifth_key": 28
}

Answer

As @dbf said in the comment section, I have to handle empty rows. I have checked several times in the database, and maybe I missed that one blank row. Anyway, this is how I handle those values:

if (!isset($data->json_data->second_key)) {
    $second_key = '-';
} else {
    $second_key = $data->json_data->second_key;
}

return [
     $data->id,
     $data->title,
     $data->status,
     $data->gender,
     $second_key
];