I have below code to map the fileds with projection.

  private static ProjectionOperation getProjectionOperation() {
      
      Cond conditional =  ConditionalOperators.when(Criteria.where("joined.isHeaderDocument").is(Boolean.TRUE)).thenValueOf("documentID").otherwise(null);
        ProjectionOperation projectOperation = Aggregation.project(
                 .and("doc").as("relationshipNumber")
                 .and(conditional).as("headerForm");
                 
                
        return projectOperation;

I have to return documentID value when isHeaderDocument is true otherwise i should not map the filed “headerForm” . I am getting exception like “null values not supported for conditional operators”. Can any on please help