zig: assert there is an exception when .zero is returned

[nektro]

cc #15141

[robobun]

❌ @Jarred-Sumner, your commit 72b8b89 has 13 failures in #6768:

test/js/bun/http/bun-serve-static.test.ts - timeout on 🐧 3.20 x64

test/integration/next-pages/test/dev-server.test.ts - 1 failing on 🐧 3.20 x64

test/integration/next-pages/test/dev-server.test.ts - 1 failing on 🐧 3.20 x64-baseline

test/v8/v8.test.ts - 22 failing on 🐧 3.20 aarch64

test/v8/v8.test.ts - 22 failing on 🐧 3.20 x64

test/v8/v8.test.ts - 22 failing on 🐧 3.20 x64-baseline

test/js/node/test/parallel/fs-watch-recursive-linux-parallel-remove.test.js - 1 failing on 🐧 12 x64-baseline

test/js/node/test/parallel/fs-watch-recursive-linux-parallel-remove.test.js - 1 failing on 🐧 22.04 x64-baseline

test/js/node/test/parallel/fs-watch-recursive-linux-parallel-remove.test.js - 1 failing on 🐧 22.04 x64

test/js/node/test/parallel/fs-watch-recursive-linux-parallel-remove.test.js - 1 failing on 🐧 3.20 aarch64

test/js/node/test/parallel/fs-watch-recursive-linux-parallel-remove.test.js - 1 failing on 🐧 3.20 x64

test/js/node/test/parallel/fs-watch-recursive-linux-parallel-remove.test.js - 1 failing on 🐧 3.20 x64-baseline

test/js/bun/http/serve.test.ts - segmentation fault on 🐧 3.20 aarch64

test/js/bun/http/serve.test.ts - segmentation fault on 🐧 3.20 x64

test/js/bun/http/serve.test.ts - segmentation fault on 🐧 3.20 x64-baseline

test/cli/hot/hot.test.ts - timeout on 🐧 22.04 x64

test/cli/hot/hot.test.ts - 1 failing on 🐧 3.20 x64-baseline

test/js/node/child_process/child_process.test.ts - 1 failing on 🐧 3.20 aarch64

test/js/node/child_process/child_process.test.ts - 1 failing on 🐧 3.20 x64

test/js/node/child_process/child_process.test.ts - 1 failing on 🐧 3.20 x64-baseline

test/cli/install/bun-link.test.ts - 4 failing on 🐧 3.20 aarch64

test/cli/install/bun-link.test.ts - 4 failing on 🐧 3.20 x64

test/cli/install/bun-link.test.ts - 4 failing on 🐧 3.20 x64-baseline

test/js/web/fetch/fetch.stream.test.ts - 1 failing on 🍎 14 x64

test/integration/next-pages/test/next-build.test.ts - 1 failing on 🐧 22.04 aarch64

test/integration/next-pages/test/next-build.test.ts - 1 failing on 🐧 22.04 x64-baseline

test/integration/next-pages/test/next-build.test.ts - 1 failing on 🐧 22.04 x64

test/js/web/fetch/fetch.test.ts - 1 failing on 🍎 14 aarch64

test/js/node/watch/fs.watch.test.ts - 3 failing on 🍎 14 aarch64

test/js/web/fetch/fetch.tls.test.ts - 1 failing on 🍎 13 aarch64