Fix "no-void" lint issues
Fix "no-void" lint issues

Use the global variable instead of using `void 0` to obtain `undefined`.

For background information, see the description of the `void` operator:
https://developer.mozilla.org/docs/Web/JavaScript/Reference/Operators/void

schul-cloud/schulcloud-server,schul-cloud/schulcloud-server,schul-cloud/schulcloud-server