### 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(false);
	if (!initialized) {
		WARN_PRINT_ONCE("Attempting to access theme items too early; prefer NOTIFICATION_POSTINITIALIZE and NOTIFICATION_THEME_CHANGED");
	}
	if (p_theme_type == StringName() || p_theme_type == get_class_name() || p_theme_type == theme_type_variation) {
		if (has_theme_stylebox_override(p_name)) {
			return true;
		}
	}
	List<StringName> theme_types;
	theme_owner->get_theme_type_dependencies(this, p_theme_type, &theme_types);
	return theme_owner->has_theme_item_in_types(Theme::DATA_TYPE_STYLEBOX, p_name, theme_types);
}
bool Window::has_theme_font(const StringName &p_name, const StringName &p_theme_type) const {
	ERR_READ_THREAD_GUARD_V(false);
	if (!initialized) {
		WARN_PRINT_ONCE("Attempting to access theme items too early; prefer NOTIFICATION_POSTINITIALIZE and NOTIFICATION_THEME_CHANGED");
	}
	if (p_theme_type == StringName() || p_theme_type == get_class_name() || p_theme_type == theme_type_variation) {
		if (has_theme_font_override(p_name)) {
			return true;
		}
	}
	List<StringName> theme_types;
	theme_owner->get_theme_type_dependencies(this, p_theme_type, &theme_types);
	return theme_owner->has_theme_item_in_types(Theme::DATA_TYPE_FONT, p_name, theme_types);
}
bool Window::has_theme_font_size(const StringName &p_name, const StringName &p_theme_type) const {