I want to have a 2-click solution for a OSM map. Ifound this solution here: https://github.com/in2code-de/in2iframeconsent They offer an example there, which I'ld expect to work. So I've copied the folders "example" and "src" to my Apache server, and added jquery to the example html file. On displaying the file in chromium there is an error:

Uncaught TypeError: Cannot read properties of null (reading 'addEventListener')
    at iframeSwitchListener (in2iframeconsent.js:36)
    at IframeSwitch.initialize (in2iframeconsent.js:16)
    at in2iframeconsent.js:232

Would someone be so kind as to tell me how to make it work? (Javascript Noob here, sorry)