feat(api): return better error message on missing embedding

I had a setup where my embedding model didn't reply properly
and had a really hard time figuring out where
"NoneType object is not iterable" comes from.
With this error message, it should be easier to find the problem.

Author: schuellerf

src/openai/resources/embeddings.py

@@ -112,6 +112,9 @@ def parser(obj: CreateEmbeddingResponse) -> CreateEmbeddingResponse:
                 # don't modify the response object if a user explicitly asked for a format
                 return obj
 
+            if obj.data is None:
+                raise ValueError("No embedding data received")
+
             for embedding in obj.data:
                 data = cast(object, embedding.embedding)
                 if not isinstance(data, str):