Codeigniter在获取对象的属性时获取非对象错误

I'm trying to get some information of an object. When I var_dump it, I get this:

var_dump($data)

object(stdClass)#44 (3) { 
    ["front_image"]=> string(19) "1424188887front.jpg" 
    ["back_image"]=> string(18) "1424188887back.jpg" 
    ["detail_file"]=> string(16) "1424188887detail.pdf" 
}

I'm trying to get the front image with

echo $data->front_image;

It echos 1424188887front.jpg followed by

A PHP Error was encountered

Severity: Notice
Message: Trying to get property of non-object
Filename: test.php  
Line Number: 198

I'm not sure what's going on. The information is printed without a problem.

The information was actually being passed in through an array with multiple $data objects.

One of them was missing a front_image property so that was why it was spitting out an error.