Seafile problem: OperationalError: no such table: notifications_notification

Hi. I have got a problem with my seafile server on Raspberry Pi with Raspbian. It is just crashed and unavailable for app and web. I found this in seahub_django_request.log:

2016-10-20 19:31:19,483 [ERROR] django.request:256 handle_uncaught_exception Internal Server Error: /
Traceback (most recent call last):
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/core/handlers/base.py”, line 108, in get_response
response = middleware_method(request)
File “/home/pi/seafile-server-6.0.4/seahub/seahub/base/middleware.py”, line 58, in process_request
self.get_from_db()
File “/home/pi/seafile-server-6.0.4/seahub/seahub/base/middleware.py”, line 51, in get_from_db
refresh_cache()
File “/home/pi/seafile-server-6.0.4/seahub/seahub/notifications/utils.py”, line 11, in refresh_cache
NOTIFICATION_CACHE_TIMEOUT)
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/core/cache/backends/filebased.py”, line 58, in set
f.write(zlib.compress(pickle.dumps(value), -1))
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/models/query.py”, line 135, in reduce
return super(QuerySet, self).reduce()
File “/usr/lib/python2.7/copy_reg.py”, line 84, in _reduce_ex
dict = getstate()
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/models/query.py”, line 95, in getstate
self._fetch_all()
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/models/query.py”, line 965, in _fetch_all
self._result_cache = list(self.iterator())
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/models/query.py”, line 238, in iterator
results = compiler.execute_sql()
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/models/sql/compiler.py”, line 840, in execute_sql
cursor.execute(sql, params)
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/backends/utils.py”, line 64, in execute
return self.cursor.execute(sql, params)
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/utils.py”, line 98, in exit
six.reraise(dj_exc_type, dj_exc_value, traceback)
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/backends/utils.py”, line 64, in execute
return self.cursor.execute(sql, params)
File “/home/pi/seafile-server-6.0.4/seahub/thirdpart/Django-1.8.10-py2.7.egg/django/db/backends/sqlite3/base.py”, line 318, in execute
return Database.Cursor.execute(self, query, params)
OperationalError: no such table: notifications_notification

I don’t know what to do. Thanks for any help.
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What did you do before the error happen? This will help to know the cause.