check if hasattr reasoning_content

Author: Ddper

Diff for: src/agents/models/openai_chatcompletions.py

@@ -208,8 +208,10 @@ async def stream_response(
                     continue
 
                 delta = chunk.choices[0].delta
-                reasoning_content = getattr(delta, "reasoning_content")
-                content = reasoning_content if reasoning_content else delta.content
+                if hasattr(delta, "reasoning_content"):
+                    content = delta.reasoning_content if delta.reasoning_content else delta.content
+                else:
+                    content = delta.content
 
                 # Handle text
                 if content: