Fix de stormvloed aan deprecation errors

[NathanHuisman]

htmlspecialchars kan geen null meer aannemen, PHP 8 wordt super boos >:(

Elke request naar /corvee/beheer genereert 1MB aan logs

[sentry-io[bot]]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: lib/view/Icon.php

Function	Unhandled Issue
CsrDelft\view\Icon::getTag	ErrorException: Deprecated: htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated ... Event Count: 2.5k

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[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud