fix: guard docStoreConn.delete with index_exist in parse and stop_parsing (#15876)

## What problem does this PR solve?

Closes #15874

Both the `POST /api/v1/datasets/<dataset_id>/chunks` (re-parse) and
`DELETE /api/v1/datasets/<dataset_id>/chunks` (stop-parsing) handlers
called `settings.docStoreConn.delete` unconditionally. When the
tenant/dataset index has not been created yet — fresh dataset, first
parse interrupted before any chunks were indexed, or index manually
removed — the delete call throws and the handler returns HTTP 500
**after** the document state was already mutated (RUNNING with zeroed
counters for the parse path; CANCEL with zeroed counters for the stop
path), leaving the document in an inconsistent state.

The newer `parse_documents` path in `document_api.py` already uses
`index_exist` before deleting:



## How to fix?

Apply the same `index_exist` guard to both call sites in `chunk_api.py`:

- **`parse`** (POST path, line ~192): guard the delete before
`TaskService.filter_delete`.
- **`stop_parsing`** (DELETE path, line ~242): guard the delete after
`DocumentService.update_by_id`.

Both sites already have the correct `search.index_name(tenant_id)` and
`dataset_id` parameters; the guard is a one-line addition at each site.

## Type of change

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

---------

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Wang Qi <wangq8@outlook.com>

api/apps/restful_apis/chunk_api.py

@@ -190,7 +190,16 @@ async def parse(tenant_id, dataset_id):
             == 0
         ):
             return get_error_data_result("Can't parse document that is currently being processed")
-        settings.docStoreConn.delete({"doc_id": id}, search.index_name(tenant_id), dataset_id)
+        index_name = search.index_name(tenant_id)
+        if settings.docStoreConn.index_exist(index_name, dataset_id):
+            settings.docStoreConn.delete({"doc_id": id}, index_name, dataset_id)
+        else:
+            logging.info(
+                "Skipping chunk delete during parse for doc %s: index %s/%s does not exist",
+                id,
+                index_name,
+                dataset_id,
+            )
         TaskService.filter_delete([Task.doc_id == id])
         e, doc = DocumentService.get_by_id(id)
         doc = doc.to_dict()
@@ -240,7 +249,16 @@ async def stop_parsing(tenant_id, dataset_id):
         cancel_all_task_of(id)
         info = {"run": "2", "progress": 0, "chunk_num": 0}
         DocumentService.update_by_id(id, info)
-        settings.docStoreConn.delete({"doc_id": doc[0].id}, search.index_name(tenant_id), dataset_id)
+        index_name = search.index_name(tenant_id)
+        if settings.docStoreConn.index_exist(index_name, dataset_id):
+            settings.docStoreConn.delete({"doc_id": doc[0].id}, index_name, dataset_id)
+        else:
+            logging.info(
+                "Skipping chunk delete during stop_parsing for doc %s: index %s/%s does not exist",
+                doc[0].id,
+                index_name,
+                dataset_id,
+            )
         success_count += 1
     if duplicate_messages:
         if success_count > 0: