update vllm_worker.py

[jbding]

Why are these changes needed?

• The vllm_worker code does not catch exceptions: when I check vllm's SamplingParams function, there is parameter verification and the error ValueError is thrown out.
• Because there is no capture, the semaphore is not released after the code execution fails, causing the model to fail to work.

Related issue number (if applicable)

Fix #3328

Checks

• [ ✓] I've run format.sh to lint the changes in this PR.
• [ ✗] I've included any doc changes needed.
• [ ✓] I've made sure the relevant tests are passing (if applicable).