Steps to reproduce the issue

On a patchtester based on current master branch, i.e. including all corrections merged since the last 4.0 beta, apply PR joomla/joomla-cms#25117.

This is a PR which changes composer.json and composer-lock.json.

Expected result

Either patch applied, or some error message that it isn't allowed for this or that reason.

Actual result

Backend and frontend are white pages immediately after having clicked "apply", or in my last test the patchtester has shown the patch applied, but when navigating to somewhere else in backend it was blank page.

In PHP error log:

PHP Warning:  require(/home/richard/lamp/public_html/joomla-cms-4.0-dev/libraries/vendor/composer/../zendframework/zend-diactoros/src/functions/create_uploaded_file.php): failed to open stream: No such file or directory in /home/richard/lamp/public_html/joomla-cms-4.0-dev/libraries/vendor/composer/autoload_real.php on line 66, referer: https://www.joomla-40-dev.vmkubu02.vmnet2.local/administrator/index.php?option=com_patchtester&view=pulls
PHP Fatal error:  require(): Failed opening required '/home/richard/lamp/public_html/joomla-cms-4.0-dev/libraries/vendor/composer/../zendframework/zend-diactoros/src/functions/create_uploaded_file.php' (include_path='.:/usr/share/php') in /home/richard/lamp/public_html/joomla-cms-4.0-dev/libraries/vendor/composer/autoload_real.php on line 66, referer: https://www.joomla-40-dev.vmkubu02.vmnet2.local/administrator/index.php?option=com_patchtester&view=pulls

Running composer install and npm ci or removing the libraries/autoload_psr4.php file or all of that in combination doesn't fix it.

System information (as much as possible)

PHP 7.3 on Linux.

Additional comments

It could be that there is some systematic error when having PR's which change composer dependencies.