fix: added Handling for null init in VariableDeclarator

[wattanx]

🔗 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

I've added a process to return if the 'init' of 'VariableDeclarator' is null, as there are cases when it can be null.
We would like to avoid walk what we don't need, but it is currently difficult.

For example

let value

definePageMeta({
  layout: 'custom'
})

📝 Checklist

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