fix(core): tolerate missing related index labels

Author: contrueCT

hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/backend/tx/GraphIndexTransaction.java

@@ -1564,8 +1564,13 @@ private static Set<IndexLabel> relatedIndexLabels(HugeElement element) {
         Set<Id> indexLabelIds = element.schemaLabel().indexLabels();
 
         for (Id id : indexLabelIds) {
-            IndexLabel indexLabel = element.graph().indexLabel(id);
-            indexLabels.add(indexLabel);
+            try {
+                IndexLabel indexLabel = element.graph().indexLabel(id);
+                indexLabels.add(indexLabel);
+            } catch (IllegalArgumentException e) {
+                LOG.debug("Skip missing related index label '{}' of element {}",
+                          id, element.id(), e);
+            }
         }
         return indexLabels;
     }