title: Codeigniter weird form_dropdown bug mixed index
body: <p>I am having a wierd issue with the form_dropdown helper in codeigniter version 2.1.3.</p>
  
  <p>The following code: </p>
  
  <pre><code>print_r($country_options);
  
  echo form_label('Country:','country') . 
  form_dropdown('country',$country_options, 0);
  ...
  </code></pre>
  
  <p>Outputs </p>
  
  <pre><code>Array ( [0] =&gt; All [Australia] =&gt; Australia )
  
  &lt;label for="country"&gt;Country:&lt;/label&gt;
  &lt;select name="country"&gt;
  &lt;option value="0" selected="selected"&gt;All&lt;/option&gt;
  &lt;option value="Australia" selected="selected"&gt;Australia&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>What am I not seeing? </p>
  
  <p>The problem that instead of only the dropdown 'All' being selected as is set in the third parameter of the form_dropdown function, both dropdown options are being selected even though the second option has a key of 'Australia'</p>