Fix mypy error: len() on Optional[str] in __repr__

Author: neluca

tinybpe/tokenizer.py

@@ -230,8 +230,7 @@ def stream_decode_reset(self) -> None:
     def __repr__(self) -> str:
         """Return a concise string representation."""
         has_remap = self._bytes_maps is not None
-        has_special = self._special_tokens is not None
-        n_special = len(self._special_tokens) if has_special else 0
+        n_special = len(self._special_tokens) if self._special_tokens is not None else 0
         return f"Tokenizer(n_vocab={self.n_vocab}, byte_remap={has_remap}, special_tokens={n_special})"
 
     @property