Shipping module unable to register an error

Shipping module unable to register an error on checkout_shipping header
<a href='#crh-start'></a><a href='#crh-data-%7B%22processed%22%3A%20%5B%22https%3A//github.com/zencart/zc-v1-series/pull/150%23issuecomment-54875498%22%2C%20%22https%3A//github.com/zencart/zc-v1-series/pull/150%23issuecomment-55200973%22%2C%20%22https%3A//github.com/zencart/zc-v1-series/pull/150%23issuecomment-55298548%22%5D%2C%20%22comments%22%3A%20%7B%22General%20Comment%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/zencart/zc-v1-series/pull/150%23issuecomment-54875498%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22Wondering%20if%20there%20might%20be%20regression%20issues%20here.%20While%20the%20change%20looks%20good%2C%20I%27d%20want%20to%20test%20it%20against%20all%20the%20other%20built-in%20shipping%20modules%20to%20be%20sure%20that%20some%20don%27t%20mistakenly%20never%20return%20a%20multidimensional%20array%20where%20the%20%5B0%5D%20element%20might%20not%20actually%20exist.%22%2C%20%22created_at%22%3A%20%222014-09-08T19%3A41%3A07Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/404472%3Fv%3D2%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/drbyte%22%7D%7D%2C%20%7B%22body%22%3A%20%22%3A%2B1%3A%20%5B%60isset%60%5D%28http%3A//php.net/manual/en/function.isset.php%29%20works%20on%20multi-dimensional%20arrays%20beginning%20with%20the%20first%20dimension%20on%20down.%5Cr%5Cn%60%60%60php%5Cr%5Cn%24a%20%3D%20array%28%27test%27%20%3D%3E%201%2C%20%27hello%27%20%3D%3E%20NULL%2C%20%27pie%27%20%3D%3E%20array%28%27a%27%20%3D%3E%20%27apple%27%29%29%3B%5Cr%5Cnvar_dump%28isset%28%24a%5B%27cake%27%5D%5B%27a%27%5D%5B%27b%27%5D%29%29%3B%20%20//%20FALSE%5Cr%5Cn%60%60%60%22%2C%20%22created_at%22%3A%20%222014-09-10T23%3A44%3A30Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/1590605%3Fv%3D2%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/texdc%22%7D%7D%2C%20%7B%22body%22%3A%20%22%3Ashipit%3A%22%2C%20%22created_at%22%3A%20%222014-09-11T17%3A28%3A37Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/227354%3Fv%3D2%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/zcwilt%22%7D%7D%5D%2C%20%22title%22%3A%20%22General%20Comment%22%7D%7D%2C%20%22approved%22%3A%20%7B%22https%3A//github.com/zcwilt%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/227354%3Fv%3D2%22%7D%7D%7D'></a>
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- [x] <a href='#crh-comment-General Comment'></a> <img src='http://www.codereviewhub.com/site/github-completed.png' height=16 width=60>&nbsp;<b><a href='https://github.com/zencart/zc-v1-series/pull/150#issuecomment-54875498'>General Comment</a></b>
- <a href='https://github.com/drbyte'><img border=0 src='https://avatars.githubusercontent.com/u/404472?v=2' height=16 width=16'></a> Wondering if there might be regression issues here. While the change looks good, I'd want to test it against all the other built-in shipping modules to be sure that some don't mistakenly never return a multidimensional array where the [0] element might not actually exist.
- <a href='https://github.com/texdc'><img border=0 src='https://avatars.githubusercontent.com/u/1590605?v=2' height=16 width=16'></a> :+1: [`isset`](http://php.net/manual/en/function.isset.php) works on multi-dimensional arrays beginning with the first dimension on down.
```php
$a = array('test' => 1, 'hello' => NULL, 'pie' => array('a' => 'apple'));
var_dump(isset($a['cake']['a']['b']));  // FALSE
```


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