fix no language attr value in mesh (#2182)

oap-server/server-storage-plugin/storage-elasticsearch-plugin/src/main/java/org/apache/skywalking/oap/server/storage/plugin/elasticsearch/query/MetadataQueryEsDAO.java

@@ -216,6 +216,8 @@ public class MetadataQueryEsDAO extends EsDAO implements IMetadataQueryDAO {
                         serviceInstance.getAttributes().add(new Attribute(ServiceInstanceInventory.PropertyUtil.IPV4S, ipv4));
                     }
                 }
+            } else {
+                serviceInstance.setLanguage(Language.UNKNOWN);
             }
 
             serviceInstances.add(serviceInstance);

oap-server/server-storage-plugin/storage-jdbc-hikaricp-plugin/src/main/java/org/apache/skywalking/oap/server/storage/plugin/jdbc/h2/dao/H2MetadataQueryDAO.java

@@ -241,6 +241,8 @@ public class H2MetadataQueryDAO implements IMetadataQueryDAO {
                                 serviceInstance.getAttributes().add(new Attribute(ServiceInstanceInventory.PropertyUtil.IPV4S, ipv4));
                             }
                         }
+                    } else {
+                        serviceInstance.setLanguage(Language.UNKNOWN);
                     }
 
                     serviceInstances.add(serviceInstance);