Bug: Cannot read properties of null (reading 'length') when using BYOK

[doggy8088]

Describe the bug

When using BYOK (Bring Your Own Key) in the Copilot CLI, I encounter the following error: Cannot read properties of null (reading 'length').

Affected version

GitHub Copilot CLI 1.0.64.

Steps to reproduce the behavior

1. Open Copilot CLI with the following command:

   COPILOT_PROVIDER_TYPE=openai COPILOT_PROVIDER_WIRE_API=completions COPILOT_PROVIDER_BASE_URL=https://api.mistral.ai/v1 COPILOT_PROVIDER_API_KEY=$MISTRAL_API_KEY COPILOT_MODEL=mistral-medium-latest COPILOT_PROVIDER_MAX_PROMPT_TOKENS=262144 COPILOT_PROVIDER_MAX_OUTPUT_TOKENS=262144 copilot --yolo --log-level all --log-dir logs/

2. Send prompt

   hi
   

Expected behavior

No error

Additional context

process-1782304659429-43157.log