16:52:33.846 ERROR d.t.a.c.ControllerExceptionHelper - com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Missing type id when trying to resolve subtype of [simple type, class de.thm.arsnova.model.ChoiceAnswer]: missing type id property 'format'
 at [Source: UNKNOWN; line: -1, column: -1]
org.ektorp.DbAccessException: com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Missing type id when trying to resolve subtype of [simple type, class de.thm.arsnova.model.ChoiceAnswer]: missing type id property 'format'
 at [Source: UNKNOWN; line: -1, column: -1]
	at org.ektorp.util.Exceptions.propagate(Exceptions.java:19)
Caused by: com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Missing type id when trying to resolve subtype of [simple type, class de.thm.arsnova.model.ChoiceAnswer]: missing type id property 'format'
 at [Source: UNKNOWN; line: -1, column: -1]
	at com.fasterxml.jackson.databind.exc.InvalidTypeIdException.from(InvalidTypeIdException.java:43)
16:52:33.846 ERROR d.t.a.c.ControllerExceptionHelper -
java.lang.NullPointerException: null
	at de.thm.arsnova.service.AnswerServiceImpl.getAnswerByContentIdAndUserIdAndRound(AnswerServiceImpl.java:315)
16:52:33.849 ERROR d.t.a.c.ControllerExceptionHelper - com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Missing type id when trying to resolve subtype of [simple type, class de.thm.arsnova.model.ChoiceAnswer]: missing type id property 'format'
 at [Source: UNKNOWN; line: -1, column: -1]
org.ektorp.DbAccessException: com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Missing type id when trying to resolve subtype of [simple type, class de.thm.arsnova.model.ChoiceAnswer]: missing type id property 'format'
 at [Source: UNKNOWN; line: -1, column: -1]
	at org.ektorp.util.Exceptions.propagate(Exceptions.java:19)
Caused by: com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Missing type id when trying to resolve subtype of [simple type, class de.thm.arsnova.model.ChoiceAnswer]: missing type id property 'format'
 at [Source: UNKNOWN; line: -1, column: -1]