Description:
------------
Since php 7.4.6, When nesting several `yield from`, the `\Generator::valid` methods return true while the Generator stay open after the last item. (calling `Generator::valid` return once true after the last item.

Test script:
---------------
<?php

function foo()
{
    yield from ['foo', 'bar'];
}

function bar()
{
    yield from foo();
}

function countGenerator($generator)
{
    for ($count = 0; $generator->valid(); $generator->next()) {
        ++$count;
    }

    return $count;
}

var_dump(countGenerator(foo()));
var_dump(countGenerator(bar()));


Expected result:
----------------
int(2)
int(2)


Actual result:
--------------
int(2)
int(3)