fix(renderer): support modifying el in beforeMount

[zenotsai]

Summary

This merge request updates the condition in the renderer to support modifying the el property during the beforeMount lifecycle hook.

Changes

• Changed the condition from if (el && hydrateNode) to if (initialVNode.el && hydrateNode) in renderer.ts.

Reason

The modification allows developers to change the el property in the beforeMount lifecycle hook, providing more flexibility in the rendering process.

Testing

• Verified that the el property can be modified in the beforeMount hook without causing issues during hydration.

[edison1105]

This change will cause the following issues:

• If el does not exist, adding el in beforeMount will cause the logic that should be mount to become hydrate.
• If el exists, modifying el in beforeMount will cause a hydration mismatch.