fix(openai): Check response text is present to avoid AttributeError (#5081)

Verify that messages are not null before calling `model_dump()` on message objects in chat completion choices. Gemini's API can return `null` values in these fields.

Closes #5071

Author: alexander-alderman-webb

sentry_sdk/integrations/openai.py

@@ -243,7 +243,11 @@ def _set_output_data(span, response, kwargs, integration, finish_span=True):
 
     if hasattr(response, "choices"):
         if should_send_default_pii() and integration.include_prompts:
-            response_text = [choice.message.model_dump() for choice in response.choices]
+            response_text = [
+                choice.message.model_dump()
+                for choice in response.choices
+                if choice.message is not None
+            ]
             if len(response_text) > 0:
                 set_data_normalized(span, SPANDATA.GEN_AI_RESPONSE_TEXT, response_text)