django.db.utils.IntegrityError: NOT NULL constraint failed: chat_chat2.message - django

Question

I try to built basic chat application in django using jquery. In my post view of views.py, I successfully get the message data but some how in c.save() i got an below error. i also try to debug passing default value but getting same error. i can't make it as a not null constraint.
models.py
from django.db import models
from django.contrib.auth.models import User
# Create your models here.
class Chat2(models.Model):
user = models.ForeignKey(User)
message = models.CharField(max_length=500)
def __unicode__(self):
return self.message
chat.js
$('#msg_f').on('submit',function(event) {
event.preventDefault();
$.ajax({
datatype:"json",
url : '/login/post/',
type: 'POST',
data:{msgbox : $('#msg_box').val()},
success : function(data){
$('#msg_box').val('');
$('#msg_b').append('<div class="msg_right"><p class="msg">'+data.msgbox+'</p></div>');
}
});
});
views.py
def post(request):
if request.method=="POST":
msg = request.POST.get('msgbox',None)
c = Chat2(user=request.user,message=msg)
if msg != '':
c.save()
return JsonResponse({'msg':msg,'user':c.user.username})
else:
return HttpResponse("request must be post")
Error
[24/Jun/2017 09:21:45] "GET /login/login/chat_home/ HTTP/1.1" 200 3216
Internal Server Error: /login/post/
Traceback (most recent call last):
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\backends\utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\backends\sqlite3\base.py", line 328, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.IntegrityError: NOT NULL constraint failed: chat_chat2.message
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\core\handlers\exception.py", line 41, in inner
response = get_response(request)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\core\handlers\base.py", line 187, in _get_response
response = self.process_exception_by_middleware(e, request)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\core\handlers\base.py", line 185, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\django-tuto\login\chat\views.py", line 40, in post
c.save()
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\models\base.py", line 806, in save
force_update=force_update, update_fields=update_fields)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\models\base.py", line 836, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\models\base.py", line 922, in _save_table
result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\models\base.py", line 961, in _do_insert
using=using, raw=raw)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\models\manager.py", line 85, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\models\query.py", line 1063, in _insert
return query.get_compiler(using=using).execute_sql(return_id)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\models\sql\compiler.py", line 1099, in execute_sql
cursor.execute(sql, params)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\backends\utils.py", line 80, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\backends\utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\utils\six.py", line 685, in reraise
raise value.with_traceback(tb)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\backends\utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "C:\Users\Harshit\Anaconda3\lib\site-packages\django\db\backends\sqlite3\base.py", line 328, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: NOT NULL constraint failed: chat_chat2.message