### 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.
ERR_READ_THREAD_GUARD_V(Ref<Theme>());
	return theme;
}
void Window::_theme_changed() {
	if (is_inside_tree()) {
		theme_owner->propagate_theme_changed(this, this, true, false);
	}
}
void Window::_notify_theme_override_changed() {
	if (!bulk_theme_override && is_inside_tree()) {
		notification(NOTIFICATION_THEME_CHANGED);
	}
}
void Window::_invalidate_theme_cache() {
	theme_icon_cache.clear();
	theme_style_cache.clear();
	theme_font_cache.clear();
	theme_font_size_cache.clear();
	theme_color_cache.clear();
	theme_constant_cache.clear();
}
void Window::_update_theme_item_cache() {