Fix: guard missing task language (#15136)

### What problem does this PR solve?

guard missing task language

### Type of change

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

rag/app/naive.py

@@ -799,6 +799,7 @@ def chunk(filename, binary=None, from_page=0, to_page=MAXIMUM_PAGE_NUMBER, lang=
     urls = set()
     url_res = []
 
+    lang = lang or "Chinese"
     is_english = lang.lower() == "english"  # is_english(cks)
     parser_config = kwargs.get("parser_config", {"chunk_token_num": 512, "delimiter": "\n!?。；！？", "layout_recognize": "DeepDOC", "analyze_hyperlink": True})
 

rag/svr/task_executor.py

@@ -299,13 +299,14 @@ async def build_chunks(task, progress_callback):
 
     try:
         async with chunk_limiter:
+            task_language = task.get("language") or "Chinese"
             cks = await thread_pool_exec(
                 chunker.chunk,
                 task["name"],
                 binary=binary,
                 from_page=task["from_page"],
                 to_page=task["to_page"],
-                lang=task["language"],
+                lang=task_language,
                 callback=progress_callback,
                 kb_id=task["kb_id"],
                 parser_config=parser_config_for_chunk,
@@ -1286,7 +1287,9 @@ async def do_handle_task(task):
     task_to_page = task["to_page"]
     task_tenant_id = task["tenant_id"]
     task_embedding_id = task["embd_id"]
-    task_language = task["language"]
+    task_language = task.get("language") or "Chinese"
+    if not task.get("language"):
+        logging.warning("Task %s has no language set, falling back to Chinese", task_id)
     doc_task_llm_id = task["parser_config"].get("llm_id") or task["llm_id"]
     kb_task_llm_id = task['kb_parser_config'].get("llm_id") or task["llm_id"]
     task['llm_id'] = kb_task_llm_id