Codeigniter：获取错误消息Undefined property：stdClass

Question

I'm working on my program using Codeigniter. I try to count data between two dates. But i got an error like this.

A PHP Error was encountered
Severity: Notice
Message: Undefined property: stdClass::$umum
Filename: admin/periode-rekam.php
Line Number: 66

Controller :

public function perioderekam()
{
    [.....]

    $data['umum'] = $this->a_model->hitung_umum($tgl_awal,$tgl_akhir);
    $this->template->admin('admin/periode-rekam',$data);
}

Model :

public function hitung_umum($tgl_awal,$tgl_akhir)
{
    $sql ="SELECT COUNT(tb_mengambil.kode_kategori) AS total
    FROM tb_mengambil
    JOIN tb_kategori ON tb_mengambil.kode_kategori = tb_kategori.kode_kategori
    WHERE tb_mengambil.tgl_resep between '$tgl_awal' and '$tgl_akhir'
    ORDER BY tgl_resep DESC;";
    $query=$this->db->query($sql);
    return $query->result();
}

EDITED : IT SOLVED ALREADY. Here the answer.
Because i pass echo $isi->umum on my View, i need to change my query on model like this.

public function hitung_umum($tgl_awal,$tgl_akhir)
{
    $sql ="SELECT COUNT(tb_mengambil.kode_kategori) AS umum
    FROM tb_mengambil
    JOIN tb_kategori ON tb_mengambil.kode_kategori = tb_kategori.kode_kategori
    WHERE tb_mengambil.tgl_resep between '$tgl_awal' and '$tgl_akhir'
    ORDER BY tgl_resep DESC;";
    $query=$this->db->query($sql);
    return $query->result();
}

And I put code like this on my View :

<tr>
   <th colspan="8">Total Kategori Umum</th>
   <th colspan="2"><?php foreach ($umum as $isi){
                    echo ($isi->umum);}?>
   </th>
</tr>

I also tried <?php echo $umum; ?> but it also got me an error ' Array to string conversion'