gateway should reject model if model doesn't exist

[Jeffwan]

🐛 Describe the bug

I notice this problem in a testing. When I delete the pod, I notice it return 500 without additional error. Technically, it should be a 404.. it can not find the associate model.

Steps to Reproduce

No response

Expected behavior

No response

Environment

No response

[Jeffwan]

I just delete the model and try to send a request during the deletion but notice nothing returned.

[Jeffwan]

• Terminating
  

• Deleted
  

Terminating part is ok, we should clean up the dict key as well.

[Jeffwan]

terminating we should reject the request as well