title: Can not read property of undefined i18n
body: <p>When I try to pass language dynamically from select dropdown list, It shows following error
  Uncaught TypeError: Cannot read property 'properties' of undefined at changeLanguage</p>
  
  <p>Where changeLanguage is my function as follows:</p>
  
  <pre><code>function changeLanguage(lang) 
  { 
   lang = lang || "en_EN"; // if no language is set, use browser default 
   jQuery.i18n.properties({ 
   path : 'language', 
   mode : 'both', language: lang,
   name: 'Messages', 
   callback: refresh_i18n }); 
  }
  </code></pre>
  
  <p>Following are the pictures of it:</p>
  
  <p><a href="https://user-images.githubusercontent.com/20225402/28014110-119fb170-6589-11e7-926e-b3eec0f00c99.png" rel="nofollow noreferrer">Dropdown image</a></p>
  
  <p><a href="https://user-images.githubusercontent.com/20225402/28014117-17891e50-6589-11e7-8250-564ccf380d08.png" rel="nofollow noreferrer">Console error</a></p>
  
  <p>What is wrong with the code?
  Please do suggest!
  Thanks</p>
  
  <p><strong>UPDATE</strong>:
  FOR MORE EXPLANATION:
  This is my index file and initially I call it with onload it works fine.</p>
  
  <pre><code>&lt;script&gt; 
  function refresh_i18n() { 
    console.log('Some code...') 
  } 
  function changeLanguage(lang) { 
       lang = lang || "en_EN"; 
       jQuery.i18n.properties({ 
       path : 'js/libs/language', 
       mode : 'both', 
       language: lang, 
       callback: refresh_i18n 
     });
  } 
  changeLanguage("en_US"); 
  &lt;/script&gt;
  </code></pre>
  
  <p>but when i call by changing dropdown like:</p>
  
  <pre><code>$('#selectLanguage').change(function(){ 
      changeLanguage(this.value); 
  });
  </code></pre>
  
  <p>It gives above error</p>