Fix: set default chunk_token_num in html_parser (#10118)

### What problem does this PR solve?

issue:
[Bug]: Agent component (HTTP Request) "'>' not supported between
instances of 'int' and 'NoneType'"
[#10096](https://github.com/infiniflow/ragflow/issues/10096)

Change:
When the Invoke class instantiates HtmlParser without providing the
chunk_token_num parameter, the value defaults to None, leading to a
comparison error with block_token_count.

This change sets the default chunk_token_num to 512 to prevent such
errors.
### Type of change

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

Co-authored-by: BadwomanCraZY <511528396@qq.com>

deepdoc/parser/html_parser.py

@@ -37,7 +37,7 @@ TITLE_TAGS = {"h1": "#", "h2": "##", "h3": "###", "h4": "#####", "h5": "#####",
 
 
 class RAGFlowHtmlParser:
-    def __call__(self, fnm, binary=None, chunk_token_num=None):
+    def __call__(self, fnm, binary=None, chunk_token_num=512):
         if binary:
             encoding = find_codec(binary)
             txt = binary.decode(encoding, errors="ignore")