Fix: Handle the case of deleting empty blocks. Update the relevant message (#6643)

…gic to return the correct deletion message. Add handling for empty
arrays to ensure no errors occur during the deletion operation. Update
the test cases to verify the new logic.

### What problem does this PR solve?

fix this bug：https://github.com/infiniflow/ragflow/issues/6607

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

---------

Co-authored-by: wenju.li <wenju.li@deepctr.cn>

rag/utils/es_conn.py

@@ -413,7 +413,10 @@ class ESConnection(DocStoreConnection):
             chunk_ids = condition["id"]
             if not isinstance(chunk_ids, list):
                 chunk_ids = [chunk_ids]
-            qry = Q("ids", values=chunk_ids)
+            if not chunk_ids:  # when chunk_ids is empty, delete all
+                qry = Q("match_all")
+            else:
+                qry = Q("ids", values=chunk_ids)
         else:
             qry = Q("bool")
             for k, v in condition.items():