Error message

• Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 175 of /srv/mcgill-cihr-ig.ca/www/includes/entity.inc).
• Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->cacheGet() (line 388 of /srv/mcgill-cihr-ig.ca/www/includes/entity.inc).