### Godot version

4.1.dev (dc625bcbfc5b587ba8867481ee7a1f6a567c25d0)

### System information

Mageia 9, Linux

### Issue description

When importing a project in current `master`, the following error is raised for each asset that gets imported:
```
Attempting to parent and popup a dialog that already has a parent.
```

It seems to be raised once per asset, caused by the progress dialog.

CC @bruvzg

### Steps to reproduce

- Import a new project in Godot that contains importable assets, e.g. https://github.com/RPicster/godot4-demo-desert-light

### Minimal reproduction project

See above.
if (!get_parent()) {
		
		return;
	}
	
	Viewport *vp = get_parent()->get_viewport();
	Window *window = nullptr;
	while (vp) {
		window = Object::cast_to<Window>(vp);
		if (window) {
			break;
		}
		if (!vp->get_parent()) {
			break;
		}
		vp = vp->get_parent()->get_viewport();
	}
	if (window) {
		transient_parent = window;
		window->transient_children.insert(this);
		if (is_inside_tree() && is_visible() && exclusive) {
			if (transient_parent->exclusive_child == nullptr) {
				if (!is_in_edited_scene_root()) {
					transient_parent->exclusive_child = this;
				}