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Error message

• Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 175 of /var/www/diversiteitinactie.be/public_html/includes/entity.inc).
• Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->cacheGet() (line 388 of /var/www/diversiteitinactie.be/public_html/includes/entity.inc).