title: How can I store empty value in GAE LinkProperty?
body: <p>By default LinkProperty() is empty. But let us say I submit a form that stores site link in the DB field with the property LinkProperty(). This works fine so far.</p>
  
  <p>Next, I want to delete that link stored in the DB by resubmitting the form with empty site link. At this time, I get database error as follows:
  "BadValueError: link must not be empty."</p>
  
  <p>Can anyone please help with this? Code below.</p>
  
  <pre><code>###Database
  class MyDatabase(db.Model):
      site = db.LinkProperty()
  
  ###Trying to store form data in the database
  
  mydb_obj = MyDatabase.get_or_insert('abc') 
  #above line works fine
  
  mydb_obj.site = self.request.get('form_site') #works fine. 
  #Above form_site is read from form submission. It can be 'www.google.com' or it can be
  #empty as in ''
  
  mydb_obj.put() #I GET ERROR WHEN form_site = ''. 
  #"BadValueError: link must not be empty"
  </code></pre>