title: jqGrid - How to unselect the header row checkbox
body: <pre><code>Here is the scenario:
  </code></pre>
  
  <p>1.  Select all rows by checking the header row checkbox.
  2.  Unselect one row.
  3.  The header row checkbox is still checked which is invalid because not all rows are selected.</p>
  
  <p>How can I unselect the hedaer row checkbox?
  Thanks</p>