bug: examples seg fault

[RaphaelDarley]

accessing fields causes segfault

recreate:

git clone https://github.com/infinyon/node-bindgen.git
cd node-bindgen/examples/class-simple
make test

this causes

make: *** [test] Segmentation fault: 11

[digikata]

Can you provide more information about the system and node version. Reproduction on this seems to succeed w/ no test failures in CI as well as manual tests in macos and linux? node versions 18 & 20

[morenol]

This should be fixed by #259

@RaphaelDarley Can you try again using the latest changes on this PR? In case that it fails, could you describe which node version you are using and which OS?