Opening another window won't use canvas items.

### Tested versions

4.2

### System information

Windows 11

### Issue description

When I open second window (Window-node) it won't use the canvas_items and scale the nodes inside.

### Steps to reproduce

Make window with sprite and try to use canva_items inside window node.

### Minimal reproduction project (MRP)

[testing (2).zip](https://github.com/godotengine/godot/files/13965833/testing.2.zip)

Start by opening the linked minimal reproduction project in Godot 4.2 on Windows 11 and reproduce the second Window-node case with a sprite and canvas_items. No source file or test is named in the issue, so trace the window and canvas scaling path from the reproduction. Done means canvas_items work in the second window and its nodes are scaled correctly.

Written by the indexing model from the issue text.