After upgrading wallabag to 2.2, if you use SQLite for database, you may have a blank page or an internal server error (error 500). It can be due to migrations which failed.
The migrations which failed are migrations which try to create new columns on tables.
To fix this problem, please execute these commands on your webserver:
php bin/console doctrine:migration:execute 20161024212538 -e=prod
php bin/console doctrine:migration:execute 20161106113822 -e=prod