Multiple PHP 8 warnings: Argument #1 ($result) must be passed by reference

Problem/Motivation

After migrating from PHP 7.4 to PHP 8.0 we've started seeing these errors:

Warning: Drupal\agreement\AgreementHandler::Drupal\agreement\{closure}(): Argument #1 ($result) must be passed by reference, value given in Drupal\agreement\AgreementHandler->getAgreementByUserAndPath() (line 154 of modules/contrib/agreement/src/AgreementHandler.php).

Steps to reproduce

Install the module with PHP 8.0 - the warnings will appear straight away.

Proposed resolution

Get rid of unneeded passing by reference in all cases.

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.