[js] Make error friendly when isOrtFormat is undefined (#19958)
### Description
Make error friendly when isOrtFormat is undefined
(`onnxruntime.InferenceSession.create` is called with ArrayBuffer or
Uint8Array).
### Motivation and Context
I was trying to run my onnx model in WebGL EP, but it gave me the error
"Cannot read properties of null (reading 'irVersion')".
I used debugger to find that actual error is `int64 is not supported`,
but the error was invisible for me.
So I made it to show both error when isOrtFormat is undefined.
<s>I haven't written unit test yet, so I'm making it draft. (I have no
idea about how do I test this though...)</s>
[d62d942](https://github.com/microsoft/onnxruntime/pull/19958/commits/d62d9425ba7b9e5ff0d0a2ae6998dd53817d5db9)