title: EntityMalformedException: Missing bundle property on entity of type student. in entity_extract_ids()
body: <p>I create simple module named "student" , this module generate new entity is "student"
  and this is my code 
  <a href="http://www.mediafire.com/?ez48n72936i3gvh" rel="nofollow">Download here</a></p>
  
  <p>but when I add new student , I get an error message like that:</p>
  
  <blockquote>
    <p>EntityMalformedException: Missing bundle property on entity of type student. in entity_extract_ids() (line 7501 of C:\AppServ\www\drupal-7.12\includes\common.inc).</p>
  </blockquote>
  
  <p>I look through all of my code but I can't find out some thing,
  Thank alot!</p>