[php-src] PR #25417: Fix GH-25415: Segfault in FilterIterator::next() after failed parent ctor

Pull Request: https://github.com/php/php-src/pull/25417 Author: lazerg When a closed generator is passed to parent::__construct() of a dual iterator, the constructor throws after the object is already marked as constructed, so inner.iterator stays NULL. If the subclass catches the exception, spl_dual_it_next() only checked for a NULL inner iterator when do_free was 0, so next() on FilterIterator, IteratorIterator, LimitIterator and friends dereferenced it. NoRewindIterator had the same problem in valid(), key(), current() and next(). The NULL check in spl_dual_it_next() now runs in both cases, and the NoRewindIterator methods behave like the other iterators here: valid() returns false, key() and current() return NULL, and next() throws the existing "inner constructor wasn't initialized" error. Fixes #25415