Prevent NPE when delta is null in Azure OpenAI streaming#1721

geoand merged 1 commit intoquarkiverse:mainquarkiverse/quarkus-langchain4j:mainfrom

windschi3f:fix/azure-openai-streaming-null-deltawindschi3f/quarkus-langchain4j:fix/azure-openai-streaming-null-deltaCopy head branch name to clipboard