SelectOptionsImplementation fails to restore form state for 'integer' option values

[patricekaufmann]

The follwing comparison in SelectOptionsImplementation.php fails for integer option values (eg. 1) since the types don't match. Hence the form values will be lost when restoring the form state after failed validation.

 private function isOptionSelected($optionValue): bool
    {
        $elementValue = ($this->runtime->getCurrentContext())['elementValue'] ?? null;
        if ($optionValue === $elementValue) {
            return true;
        }
        if (is_array($elementValue) && in_array($optionValue, $elementValue)) {
            return true;
        }
        return false;
    }

Suggested Fix: cast $optionValue as string.