Versions: * Firefox: 126.0 * Chrome: 119.0 --- Description: Upon attempting to detect dark mode during page load, Firefox attempts to operate on the non-existent `id=darkmode` element in the `<head>`. Steps to reproduce: 1. Run `docker run`: ``` docker run --name openspeedtest -p 3000:3000 -p 3001:3001 openspeedtest/latest ``` 2. Open <http://localhost:3000/> 3. Observe a blank window (failed page load), with the following in the browser console: ``` OpenSpeedTest.com V2.5.4 Loaded! localhost:3000:131:15 Now Press the Start Button or HIT Enter. localhost:3000:132:15 The secret to living happy is giving happiness. Have a wonderful day. localhost:3000:133:15 Uncaught TypeError: c is null addEvt http://localhost:3000/assets/js/app-2.5.4.min.js line 8 > srcScript:30 jb http://localhost:3000/assets/js/app-2.5.4.min.js line 8 > srcScript:44 Start http://localhost:3000/assets/js/app-2.5.4.min.js line 8 > srcScript:51 onload http://localhost:3000/assets/js/app-2.5.4.min.js line 8 > srcScript:9 EventHandlerNonNull* http://localhost:3000/assets/js/app-2.5.4.min.js line 8 > srcScript:9 app-2.5.4.min.js line 8 > srcScript:30:282 Uncaught TypeError: nightMode is null changeSkin http://localhost:3000/assets/js/darkmode.js:2 EventListener.handleEvent* http://localhost:3000/assets/js/darkmode.js:1 darkmode.js:2:247 ``` Attempting the same page load with Chrome does not exhibit this issue. There does not appear to be a 'mode' cookie that would indicate a previous detection of dark mode. The 'matchMedia' handling in the `<head>` script does not appear to fail, but later reference to the `darkmode` element prevents further page load (and results in no interface presented in Firefox).