title: Error : "You are trying to add a non-nullable field"
body: <p>I defined below model and getting</p>
  
  <p>error : <code>You are trying to add a non-nullable field 'user' to videodata without a default; we can't do that</code></p>
  
  <p>models.py</p>
  
  <pre><code>class User(Model):
      userID = models.IntegerField()
      userName = models.CharField(max_length=40)
      email = models.EmailField()
      class Meta:
          ordering = ['userName']
          verbose_name = 'User MetaData'
          verbose_name_plural = 'Users MetaData'
      def __unicode__(self):
          return str(self.userName)
  
  class VideoData(Model):
      video = models.CharField(max_length=40)
      time  = models.IntegerField()
      user = models.ForeignKey(User, related_name='User')
      class Meta:
          verbose_name = 'User_Video MetaData'
  </code></pre>
  
  <p>Where i am doing wrong????</p>