fix - report many headers

report/src/main/java/cz/muni/fi/pa165/report/server/rest/ReportController.java

@@ -18,6 +18,7 @@ public class ReportController implements ReportApiDelegate{
     }
     HttpHeaders headers = new HttpHeaders();
     private HttpHeaders initializeHeaders(){
+        headers.clear();
         headers.add("Content-Type", "application/pdf");
         headers.add("Content-Disposition", "attachment; filename=report.pdf");
         return headers;