fix: tool-block parsing crashes on a non-string input (#1628)

src/tool_parsing.py

@@ -69,6 +69,8 @@ _TOOL_CODE_RE = re.compile(
 # fullwidth (U+FF5C) and ascii '|' in any count.
 _DSML_PIPES = r"[｜|]+"
 def _normalize_dsml(text: str) -> str:
+    if not isinstance(text, str):
+        return ""
     if "DSML" not in text:
         return text
     t = text