Fix type error in pretty printer (caused bug in associativity detection)
Fix type error in pretty printer (caused bug in associativity detection)

tias/libminizinc,jjdekker/libminizinc,nathanielbaxter/libminizinc,jjdekker/libminizinc,nathanielbaxter/libminizinc,nathanielbaxter/libminizinc,jjdekker/libminizinc,nathanielbaxter/libminizinc,jjdekker/libminizinc,tias/libminizinc