title: 'NoneType' object has no attribute 'strip' - Slugify
body: <p>I have a problem with my model in the line of slugify</p>
  
  <pre><code>from django.db import models
  from django.contrib.auth.models import User
  from django.template.defaultfilters import slugify
  
  # Create your models here.
  class Pages(models.Model):
      title = models.CharField(max_length=255)
      slug = models.SlugField(blank=True)
      content =  models.TextField(blank=True)
      publish_at = models.DateTimeField(auto_now_add=True)
      update_at = models.DateTimeField(auto_now=True)
      order =  models.IntegerField(default=0)
      type_content = models.CharField(max_length=255)
      user = models.ForeignKey(User)  
      status =models.IntegerField(default=1)
  
      def __str__(self):
          return self.title   
  
  
      def save(self,  *args, **kwargs):
  
          if not self.slug:
              self.slug = slugify(self.title)
  
          #self.user=self.request.user
          super(Pages, self).save( *args, **kwargs)
  </code></pre>
  
  <p>I tried putting the code self.slug = slugify("test of slug") and still the problem , but when he says keeps the information without problems</p>
  
  <p>this is my Error: </p>
  
  <blockquote>
    <blockquote>
      <p>Environment:</p>
    </blockquote>
    
    <p>Request Method: POST Request URL:
    <a href="http://xxx.xx.xx.xx:8000/admin/pages/pages/add/" rel="nofollow">http://xxx.xx.xx.xx:8000/admin/pages/pages/add/</a></p>
    
    <p>Django Version: 1.7.1 Python Version: 3.4.2 Installed Applications:
    ('django.contrib.admin',  'django.contrib.auth', 
    'django.contrib.contenttypes',  'django.contrib.sessions', 
    'django.contrib.messages',  'django.contrib.staticfiles',  'seo', 
    'pages',  'site_options',  'news',  'tags',  'category') Installed
    Middleware: ('django.contrib.sessions.middleware.SessionMiddleware', 
    'django.middleware.common.CommonMiddleware', 
    'django.middleware.csrf.CsrfViewMiddleware', 
    'django.contrib.auth.middleware.AuthenticationMiddleware', 
    'django.contrib.auth.middleware.SessionAuthenticationMiddleware', 
    'django.contrib.messages.middleware.MessageMiddleware', 
    'django.middleware.clickjacking.XFrameOptionsMiddleware')</p>
    
    <p>Traceback: File
    "C:\cms-rock\vrockw\lib\site-packages\django\core\handlers\base.py" in
    get_response
      111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\contrib\admin\options.py"
    in wrapper
      584.                 return self.admin_site.admin_view(view)(*args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\utils\decorators.py" in
    _wrapped_view
      105.                     response = view_func(request, *args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\views\decorators\cache.py"
    in _wrapped_view_func
      52.         response = view_func(request, *args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\contrib\admin\sites.py"
    in inner
      204.             return view(request, *args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\contrib\admin\options.py"
    in add_view
      1454.         return self.changeform_view(request, None, form_url, extra_context) File
    "C:\cms-rock\vrockw\lib\site-packages\django\utils\decorators.py" in
    _wrapper
      29.             return bound_func(*args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\utils\decorators.py" in
    _wrapped_view
      105.                     response = view_func(request, *args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\utils\decorators.py" in
    bound_func
      25.                 return func.<strong>get</strong>(self, type(self))(*args2, **kwargs2) File "C:\cms-rock\vrockw\lib\site-packages\django\db\transaction.py" in
    inner
      394.                 return func(*args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\contrib\admin\options.py"
    in changeform_view
      1405.                 self.save_model(request, new_object, form, not add) File "C:\cms-rock\cms\pages\admin.py" in save_model
      45.         obj.save() File "C:\cms-rock\cms\pages\models.py" in save
      37.         super(Pages, self).save( *args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\db\models\base.py" in
    save
      591.                        force_update=force_update, update_fields=update_fields) File
    "C:\cms-rock\vrockw\lib\site-packages\django\db\models\base.py" in
    save_base
      619.             updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields) File
    "C:\cms-rock\vrockw\lib\site-packages\django\db\models\base.py" in
    _save_table
      700.             result = self._do_insert(cls._base_manager, using, fields, update_pk, raw) File
    "C:\cms-rock\vrockw\lib\site-packages\django\db\models\base.py" in
    _do_insert
      733.                                using=using, raw=raw) File "C:\cms-rock\vrockw\lib\site-packages\django\db\models\manager.py" in
    manager_method
      92.                 return getattr(self.get_queryset(), name)(*args, **kwargs) File "C:\cms-rock\vrockw\lib\site-packages\django\db\models\query.py" in
    _insert
      921.         return query.get_compiler(using=using).execute_sql(return_id) File
    "C:\cms-rock\vrockw\lib\site-packages\django\db\models\sql\compiler.py"
    in execute_sql
      920.                 cursor.execute(sql, params) File "C:\cms-rock\vrockw\lib\site-packages\django\db\backends\utils.py" in
    execute
      85.             sql = self.db.ops.last_executed_query(self.cursor, sql, params) File
    "C:\cms-rock\vrockw\lib\site-packages\mysql\connector\django\base.py"
    in last_executed_query
      371.         return cursor.statement File "C:\cms-rock\vrockw\lib\site-packages\mysql\connector\django\base.py"
    in <strong>getattr</strong>
      147.         return getattr(self.cursor, attr) File "C:\cms-rock\vrockw\lib\site-packages\mysql\connector\cursor.py" in
    statement
      858.             return self._executed.strip()</p>
    
    <p>Exception Type: AttributeError at /admin/pages/pages/add/ Exception
    Value: 'NoneType' object has no attribute 'strip'</p>
  </blockquote>