Update src/a2a/utils/helpers.py

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: cchinchilla-dev

src/a2a/utils/helpers.py

@@ -350,8 +350,7 @@ def are_modalities_compatible(
 def _clean_empty(d: Any) -> Any:
     """Recursively remove empty strings, lists and dicts from a dictionary."""
     if isinstance(d, dict):
-        cleaned_dict = {k: _clean_empty(v) for k, v in d.items()}
-        cleaned_dict = {k: v for k, v in cleaned_dict.items() if v is not None}
+        cleaned_dict = {k: cleaned_v for k, v in d.items() if (cleaned_v := _clean_empty(v)) is not None}
         return cleaned_dict or None
     if isinstance(d, list):
         cleaned_list = [_clean_empty(v) for v in d]