runtime.InstantiateModule returns a "struct-wrapped" nil value

[edman]

Describe the bug
runtime.InstantiateModule sometimes returns a "struct-wrapped" nil value, instead of returning actual nil.

More specifically, this line https://github.com/tetratelabs/wazero/blob/main/runtime.go#L318 assigns mod and returns it implicitly on L324.

This allows code like the following to panic with a nil pointer dereference because m is nil:

m, _ := r.InstantiateModule(ctx, compiled, config)
if m != nil {      // this check passes
  defer m.Close()  // and yet this causes a nil pointer dereference
}

To Reproduce
Here is an example that mimics wazero's behavior: https://go.dev/play/p/66QShXidalq

Expected behavior
From https://go.dev/doc/faq#nil_error, the FAQ recommends:

To return a proper nil error to the caller, the function must return an explicit nil

Additional context
Found on sqlc-dev/sqlc#3759 (comment)