perf(nuxt): allow tree-shaking empty meta from build

[danielroe]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Because we output an empty object we are not able to tree-shaking empty meta objects out of the build. By setting to null instead, we can leverage rollup's ancient powers to bring order to the natural world.

Before (no minification)

  {
    name: (__nuxt_page_meta$1 == null ? void 0 : __nuxt_page_meta$1.name) ?? "about",
    path: (__nuxt_page_meta$1 == null ? void 0 : __nuxt_page_meta$1.path) ?? "/about",
    children: [],
    meta: __nuxt_page_meta$1,
    alias: (__nuxt_page_meta$1 == null ? void 0 : __nuxt_page_meta$1.alias) || [],
    redirect: (__nuxt_page_meta$1 == null ? void 0 : __nuxt_page_meta$1.redirect) || void 0,
    component: () => __vitePreload(() => import("./about.js"), true ? ["./about.js","./nuxt-link.js"] : void 0, import.meta.url).then((m) => m.default || m)
  },

After (no minification)

  {
    name: "about",
    path: "/about",
    children: [],
    meta: {},
    alias: [],
    redirect: void 0,
    component: () => __vitePreload(() => import("./about.js"), true ? ["./about.js","./nuxt-link.js"] : void 0, import.meta.url).then((m) => m.default || m)
  },

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

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