Model weight unset cause panic

[hzxuzhonghu]

What happened:

Create a InferenceModel with targetModels, but no weight set causes the epp panic.

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:

Environment:

• Kubernetes version (use kubectl version):
• Inference extension version (use git describe --tags --dirty --always):
• Cloud provider or hardware configuration:
• Install tools:
• Others: