fixed wrong attribute in pruefungs-termin

prevented prod-build, error introduced by data model change
4 jobs for master in 10 minutes and 59 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed maven-compile #824

00:02:55

 
  Test
passed frontend-test #826

00:03:55

passed maven-test #825

00:04:29

 
  Package
passed maven-package #827

00:03:33