Python: fix: exclude null file_id from input_image payload to prevent 400 sch… (#5125)

* fix: exclude null file_id from input_image payload to prevent 400 schema error (#5120)

* test: add case for additional_properties present without file_id key

---------

Co-authored-by: Sergey Borisov <sergey.borisov@dataimpact.io>

python/packages/openai/agent_framework_openai/_chat_client.py

@@ -1405,7 +1405,7 @@ class RawOpenAIChatClient(  # type: ignore[misc]
                         else "auto",
                     }
                     file_id = content.additional_properties.get("file_id") if content.additional_properties else None
-                    if file_id:
+                    if file_id is not None:
                         result["file_id"] = file_id
                     return result
                 if content.has_top_level_media_type("audio"):

python/packages/openai/tests/openai/test_openai_chat_client.py

@@ -2975,6 +2975,17 @@ def test_prepare_content_for_openai_image_content() -> None:
     assert result["detail"] == "auto"
     assert "file_id" not in result
 
+    # Test image content with additional_properties present but no file_id key
+    image_content_detail_only = Content.from_uri(
+        uri="https://example.com/basic.png",
+        media_type="image/png",
+        additional_properties={"detail": "high"},
+    )
+    result = client._prepare_content_for_openai("user", image_content_detail_only)
+    assert result["type"] == "input_image"
+    assert result["detail"] == "high"
+    assert "file_id" not in result
+
 
 def test_prepare_content_for_openai_audio_content() -> None:
     """Test _prepare_content_for_openai with audio content variations."""