Update CHANGELOG.md

Author: andreibondarev

CHANGELOG.md

@@ -12,6 +12,7 @@
 ## [Unreleased]
 - [BREAKING] [https://github.com/patterns-ai-core/langchainrb/pull/859] Add metadata support to PgVector storage
 - [BUGFIX] [https://github.com/patterns-ai-core/langchainrb/pull/939] Fix Langchain::Vectorsearch::Milvus initializer by passing :api_key
+- [BUGFIX] [https://github.com/patterns-ai-core/langchainrb/pull/953] Handle nil response in OpenAI LLM streaming
 
 ## [0.19.4] - 2025-02-17
 - [BREAKING] [https://github.com/patterns-ai-core/langchainrb/pull/894] Tools can now output image_urls, and all tool output must be wrapped by a tool_response() method