Fix: some cases Task return but not set progress (#8469)

### What problem does this PR solve?
https://github.com/infiniflow/ragflow/issues/8466
I go through the codes, current logic:
When do_handle_task raises an exception, handle_task will set the
progress, but for some cases do_handle_task internal will just return
but not set the right progress, at this cases the redis stream will been
acked but the task is running.

### Type of change

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

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

api/db/services/task_service.py

         for task in parse_task_array:
             ck_num += reuse_prev_task_chunks(task, prev_tasks, chunking_config)
         TaskService.filter_delete([Task.doc_id == doc["id"]])
-        chunk_ids = []
-        for task in prev_tasks:
-            if task["chunk_ids"]:
-                chunk_ids.extend(task["chunk_ids"].split())
-        if chunk_ids:
-            settings.docStoreConn.delete({"id": chunk_ids}, search.index_name(chunking_config["tenant_id"]),
+        pre_chunk_ids = []
+        for pre_task in prev_tasks:
+            if pre_task["chunk_ids"]:
+                pre_chunk_ids.extend(pre_task["chunk_ids"].split())
+        if pre_chunk_ids:
+            settings.docStoreConn.delete({"id": pre_chunk_ids}, search.index_name(chunking_config["tenant_id"]),
                                          chunking_config["kb_id"])
     DocumentService.update_by_id(doc["id"], {"chunk_num": ck_num})
 

rag/svr/task_executor.py

     # Either using graphrag or Standard chunking methods
     elif task.get("task_type", "") == "graphrag":
         if not task_parser_config.get("graphrag", {}).get("use_graphrag", False):
+            progress_callback(prog=-1.0, msg="Internal configuration error.")
             return
         graphrag_conf = task["kb_parser_config"].get("graphrag", {})
         start_ts = timer()
         start_ts = timer()
         chunks = await build_chunks(task, progress_callback)
         logging.info("Build document {}: {:.2f}s".format(task_document_name, timer() - start_ts))
-        if chunks is None:
-            return
         if not chunks:
             progress_callback(1., msg=f"No chunk built from {task_document_name}")
             return
             async with trio.open_nursery() as nursery:
                 for chunk_id in chunk_ids:
                     nursery.start_soon(delete_image, task_dataset_id, chunk_id)
+            progress_callback(-1, msg=f"Chunk updates failed since task {task['id']} is unknown.")
             return
         
     logging.info("Indexing doc({}), page({}-{}), chunks({}), elapsed: {:.2f}".format(task_document_name, task_from_page,