title: Is there a bug with Kendo UI grid Filter?
body: <p>I am studying Kendo UI and I've seen something really strange. I've filtered a column with the <code>Starts with</code> function and I've typed a string in the text box. But when I've clicked on <code>Filter</code>, the request was not even sent to the server and a spinner was shown forever. The error I've got was:</p>
  
  <pre><code>Uncaught TypeError: Cannot call method 'toLowerCase' of null
  </code></pre>
  
  <p>In the given column there are some null values too. Should I set their values to " " or other ad-hoc values to prevent this bug from occurring? Is that the best work-around for this issue?</p>
  
  <p>Am I right when I say that this is a Kendo UI bug? If so, is this a known issue? If so, does somebody know when will this be fixed?</p>
  
  <p>EDIT:
  Apparently if my data source contains "" instead of null at server-side, then I won't meet this bug, but it's not good to always keep an eye on my data source to change all the nulls to "". I know that the function was called to achieve case-insensitiveness, but it has a bug which makes the usage of the grid slightly uncomfortable.</p>