More robust search if schema not registered

Do not break search if a record indexed is using a schema not available in the current installation.

Record with error are flagged with indexing error and will also log an error during search

```log
 Record is indexed indexing error flag.
2024-09-20T08:59:31,591 ERROR [geonetwork.datamanager] - Record 127 / Schema 'dcat-ap' is not registered in this catalog. Install it or remove those records. Record is indexed indexing error flag.

2024-09-20T09:00:04,688 ERROR [geonetwork.index] - Failed to load metadata schema for aa122105-7db3-4a4d-9887-0ced5c2ee6b5. Error is: Schema not registered : dcat-ap
```

services/src/main/java/org/fao/geonet/api/es/EsHTTPProxy.java

@@ -651,11 +651,17 @@ private void processResponse(ServiceContext context, HttpSession httpSession,
                     ObjectNode sourceNode = (ObjectNode) doc.get("_source");
 
                     String metadataSchema = doc.get("_source").get(Geonet.IndexFieldNames.SCHEMA).asText();
-                    MetadataSchema mds = schemaManager.getSchema(metadataSchema);
-
-                    // Apply metadata schema filters to remove non-allowed fields
-                    processMetadataSchemaFilters(context, mds, doc);
-
+                    try {
+                        MetadataSchema mds = schemaManager.getSchema(metadataSchema);
+
+                        // Apply metadata schema filters to remove non-allowed fields
+                        processMetadataSchemaFilters(context, mds, doc);
+                    } catch (IllegalArgumentException e) {
+                        LOGGER.error("Failed to load metadata schema for {}. Error is: {}",
+                            getSourceString(doc, Geonet.IndexFieldNames.UUID),
+                            e.getMessage()
+                        );
+                    }
                     // Remove fields with privileges info
                     for (ReservedOperation o : ReservedOperation.values()) {
                         sourceNode.remove("op" + o.getId());