Update src/a2a/utils/task.py

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

Author: ishymko

src/a2a/utils/task.py

@@ -119,6 +119,8 @@ def apply_history_length(
     history_length = config.history_length
 
     if history_length == 0:
+        if not task.history:
+            return task
         task_copy = Task()
         task_copy.CopyFrom(task)
         task_copy.ClearField('history')