Instantiating compiled module results in nil pointer dereference in v1.8.2 but not v1.6.0

[davidmdm]

Describe the bug
Instantiating compiled module results in nil pointer dereference in v1.8.2 but not v1.6.0

To Reproduce

Clone the example repository, checkout the set-exitcode-deref-panic branch and run the tests:

git clone https://github.com/davidmdm/wzbug.git
cd wzbug
git checkout set-exitcode-deref-panic
./test.sh

Expected behavior

The module should instantiate and run properly as it did with v1.6.0 without panic.

Screenshots

Using: github.com/tetratelabs/wazero v1.6.0

---

Using: github.com/tetratelabs/wazero v1.8.2

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x1042fcbd0]

goroutine 1 [running]:
github.com/tetratelabs/wazero/internal/wasm.(*ModuleInstance).setExitCode(...)
	/Users/davidmdm/go/pkg/mod/github.com/tetratelabs/[email protected]/internal/wasm/module_instance.go:142
github.com/tetratelabs/wazero/internal/wasm.(*ModuleInstance).CloseWithExitCode(0x10449b5d8?, {0x10449c5f0?, 0x104661c00?}, 0x22e6f00?)
	/Users/davidmdm/go/pkg/mod/github.com/tetratelabs/[email protected]/internal/wasm/module_instance.go:101 +0x20
github.com/tetratelabs/wazero/internal/wasm.(*ModuleInstance).Close(0x14000074120?, {0x10449c5f0?, 0x104661c00?})
	/Users/davidmdm/go/pkg/mod/github.com/tetratelabs/[email protected]/internal/wasm/module_instance.go:96 +0x28
github.com/davidmdm/wzbug/wasi.Execute.func2()
	/Users/davidmdm/Documents/coding/exp/wazerobug/wasi/wasi.go:85 +0x34
github.com/davidmdm/wzbug/wasi.Execute({0x10449c5f0, 0x104661c00}, {{0x0, 0x0, 0x0}, {0x10449e400, 0x1400002e140}, {0x1043c3b05, 0x3}, {0x10449b538, ...}, ...})
	/Users/davidmdm/Documents/coding/exp/wazerobug/wasi/wasi.go:93 +0xd58
main.run()
	/Users/davidmdm/Documents/coding/exp/wazerobug/main.go:52 +0x428
main.main()
	/Users/davidmdm/Documents/coding/exp/wazerobug/main.go:15 +0x1c
exit status 2

Environment (please complete the relevant information):

• Go version: 1.23.4
• wazero Version: v1.6.0 & v1.8.2
• Host architecture: arm64
• Runtime mode: compiler

[davidmdm]

Note this also fails using v1.7.0

This occurs when using a compiled module with a cache directory.