fix(nuxt): ensure url is not empty string

[pi0]

🔗 Linked issue

nuxt/nuxt#13906

Reproduction: https://stackblitz.com/edit/nuxt-starter-mc3z36

❓ 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

We detect redirection happens when after router middleware, initialURL is mismatching current route's fullPath. While initialURL from req.url is /, fullPath is an empty string due to a vue-router bug. Additionally, I've added '' to '/' fallback for navigateTo to ensure this issue won't happen in other places when calling router.resolve

Other than workaround for upstream issue, this PR tries to improve path compare to avoid unnecessary navigations.

📝 Checklist

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

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