Bug: After upgrading to v1.38, token usage information isn't returned anymore for Streaming Chat completion

[marcominerva]

Describe the bug
After upgrading Semantic Kernel to v1.38, when I call IChatCompletionService.GetStreamingChatMessageContentsAsync, the last StreamingChatMessageContent does not contain token usage information anymore. If I revert back to v1.37, the information is correctly returned as expected.

To Reproduce
Steps to reproduce the behavior:

1. Update Semantic Kernel to v1.38
2. Request a chat completion using IChatCompletionService.GetStreamingChatMessageContentsAsync
3. Inspect the last StreamingChatMessageContent object that is returned
4. Usage property is null

Expected behavior
Token usage information should be returned in a consistent way in both Semantic Kernel v1.37 and v1.38.

Platform

• Language: C#
• Source: NuGet package version 1.38
• AI model: Azure OpenAI: GPT-4o-mini (2024-07-18)
• IDE: Visual Studio 2022 17.13.1
• OS: Windows 11