Fix npe, this functionality should be deprecated but we needed it for…

… the adapters backwards compatibility (#120)

processing/src/main/java/edu/harvard/hms/dbmi/avillach/hpds/processing/GenomicProcessorNoOp.java

@@ -46,16 +46,16 @@ public Optional<VariableVariantMasks> getMasks(String path, VariantBucketHolder<
 
     @Override
     public Set<String> getInfoStoreColumns() {
-        return null;
+        return Set.of();
     }
 
     @Override
     public Set<String> getInfoStoreValues(String conceptPath) {
-        return null;
+        return Set.of();
     }
 
     @Override
     public List<InfoColumnMeta> getInfoColumnMeta() {
-        return null;
+        return List.of();
     }
 }