Check tika.parser return result (#3564)

### What problem does this PR solve?

Check tika.parser return result. Close #3229

### Type of change

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

Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>

rag/app/naive.py

         callback(0.1, "Start to parse.")
         binary = BytesIO(binary)
         doc_parsed = parser.from_buffer(binary)
-        sections = doc_parsed['content'].split('\n')
-        sections = [(_, "") for _ in sections if _]
-        callback(0.8, "Finish parsing.")
+        if doc_parsed.get('content', None) is not None:
+            sections = doc_parsed['content'].split('\n')
+            sections = [(_, "") for _ in sections if _]
+            callback(0.8, "Finish parsing.")
+        else:
+            callback(0.8, f"tika.parser got empty content from {filename}.")
+            logging.warning(f"tika.parser got empty content from {filename}.")
+            return []
 
     else:
         raise NotImplementedError(