Plugin crashes WordPress with E_COMPILE_ERROR

Hi there!

This amazing plugin has worked smoothly on my site for years, but yesterday it started to trigger a fatal error on my WordPress installation.

Please can somebody advise how I might fix this?

WordPress version 5.6
Current plugin: WP RSS Aggregator (version 4.17.10)
PHP version 7.4.11

Error Details:

An error of type E_COMPILE_ERROR was caused in line 41 of the file /home/domsel1/dom.blog/wordpress/wp-content/plugins/wp-rss-aggregator/vendor/php-di/php-di/src/DI/Definition/EntryReference.php. Error message: Declaration of DI\Definition\EntryReference::getDefinition($entryName) must be compatible with DI\Definition\Helper\DefinitionHelper::getDefinition(string $entryName): DI\Definition\Definition