Can't delete answers that are marked helpful

InternalServerErrorException: { message: {"timestamp":"2020-08-17T18:21:19.226+0000","status":500,"error":"Internal Server Error","message":"could not execute statement; SQL [n/a]; constraint [helpful_answers_answer_id_fkey]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement","path":"/questions/answers/65"}, uri: https://staging.tinycampus.de/questions/answers/65 }