Bench update got error

Traceback (most recent call last):
File “/usr/lib/python3.5/runpy.py”, line 184, in _run_module_as_main
main”, mod_spec)
File “/usr/lib/python3.5/runpy.py”, line 85, in _run_code
exec(code, run_globals)
File “/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py”, line 97, in
main()
File “/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py”, line 18, in main
click.Group(commands=commands)(prog_name=‘bench’)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py”, line 764, in call
return self.main(*args, **kwargs)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py”, line 717, in main
rv = self.invoke(ctx)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py”, line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py”, line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py”, line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py”, line 555, in invoke
return callback(*args, **kwargs)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/decorators.py”, line 17, in new_func
return f(get_current_context(), *args, **kwargs)
File “/home/frappe/frappe-bench/apps/frappe/frappe/commands/init.py”, line 25, in _func
ret = f(frappe._dict(ctx.obj), *args, **kwargs)
File “/home/frappe/frappe-bench/apps/frappe/frappe/commands/site.py”, line 227, in migrate
migrate(context.verbose, rebuild_website=rebuild_website)
File “/home/frappe/frappe-bench/apps/frappe/frappe/migrate.py”, line 35, in migrate
frappe.get_attr(fn)()
File “/home/frappe/frappe-bench/apps/frappe/frappe/patches/v11_0/sync_user_permission_doctype_before_migrate.py”, line 6, in execute
frappe.reload_doc(‘core’, ‘doctype’, ‘user_permission’)
File “/home/frappe/frappe-bench/apps/frappe/frappe/init.py”, line 790, in reload_doc
return frappe.modules.reload_doc(module, dt, dn, force=force, reset_permissions=reset_permissions)
File “/home/frappe/frappe-bench/apps/frappe/frappe/modules/utils.py”, line 160, in reload_doc
return import_files(module, dt, dn, force=force, reset_permissions=reset_permissions)
File “/home/frappe/frappe-bench/apps/frappe/frappe/modules/import_file.py”, line 26, in import_files
reset_permissions=reset_permissions)
File “/home/frappe/frappe-bench/apps/frappe/frappe/modules/import_file.py”, line 31, in import_file
ret = import_file_by_path(path, force, pre_process=pre_process, reset_permissions=reset_permissions)
File “/home/frappe/frappe-bench/apps/frappe/frappe/modules/import_file.py”, line 65, in import_file_by_path
ignore_version=ignore_version, reset_permissions=reset_permissions)
File “/home/frappe/frappe-bench/apps/frappe/frappe/modules/import_file.py”, line 132, in import_doc
doc.insert()
File “/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py”, line 241, in insert
d.db_insert()
File “/home/frappe/frappe-bench/apps/frappe/frappe/model/base_document.py”, line 312, in db_insert
), list(d.values()))
File “/home/frappe/frappe-bench/apps/frappe/frappe/database.py”, line 199, in sql
self._cursor.execute(query, values)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/pymysql/cursors.py”, line 170, in execute
result = self._query(query)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/pymysql/cursors.py”, line 328, in _query
conn.query(q)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/pymysql/connections.py”, line 517, in query
self._affected_rows = self._read_query_result(unbuffered=unbuffered)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/pymysql/connections.py”, line 732, in _read_query_result
result.read()
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/pymysql/connections.py”, line 1075, in read
first_packet = self.connection._read_packet()
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/pymysql/connections.py”, line 684, in _read_packet
packet.check_error()
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/pymysql/protocol.py”, line 220, in check_error
err.raise_mysql_exception(self._data)
File “/home/frappe/frappe-bench/env/lib/python3.5/site-packages/pymysql/err.py”, line 109, in raise_mysql_exception
raise errorclass(errno, errval)
pymysql.err.IntegrityError: (1048, “Column ‘fetch_if_empty’ cannot be null”)