fix(MetadataExtractor): reset publication subsubtype to null if not present in...

https://issues.unige.ch/browse/AOU-516

AoU-ResourceServerCommon/src/main/java/ch/unige/aou/service/metadata/MetadataExtractor.java

@@ -340,6 +340,8 @@ public abstract class MetadataExtractor {
       if (subSubtype != null) {
         publication.setSubSubtype(subSubtype);
       }
+    } else {
+      publication.setSubSubtype(null);
     }
   }