102124: Avoid null pointer when checking disposition

dspace-server-webapp/src/main/java/org/dspace/app/rest/BitstreamRestController.java

@@ -208,6 +208,10 @@ public class BitstreamRestController {
     }
 
     private boolean checkFormatForContentDisposition(BitstreamFormat format) {
+        // never automatically download undefined formats
+        if (format == null) {
+            return false;
+        }
         List<String> formats = List.of((configurationService.getArrayProperty("webui.content_disposition_format")));
         boolean download = formats.contains(format.getMIMEType());
         if (!download) {