__call() proxy breaks methods with reference parameters

Problem/Motivation

When using the decorator pattern with `__call()` to proxy method calls to an inner object, methods that have parameters passed by reference (e.g., `&$complete_form`) fail with a warning.

Proposed resolution

Replace call_user_func_array() with the spread operator (...) in the __call() method:

public function __call($method, $args) {
    return $this->inner->$method(...$args);
}