Modifying GitHub Repository for Personal Use – Need Help Resolving Issues

I found a GitHub repository that is useful to me, but it lacks a feature-work on netflix I require. I opened an issue to request the feature, but the author seems currently occupied with other projects and won’t be updating it for now. Attempting to modify the code myself, I encountered some issues such as Uncaught TypeError: Cannot read properties of null (reading 'currentTime') that I couldn’t resolve. Now, I’m seeking assistance on StackOverflow to overcome these challenges.

I tried to revise the if statement to :

if (window.location.href.includes("youtube.com/watch") || window.location.href.includes("netflix.com/watch"))

and added a function to distinguish between netflix and youtube so as to get their URL

    function getVideoPlatform()
    {
        const youtubePattern = /youtube.com/watch?v=/;
        const netflixPattern = /netflix.com/watch//;

        const url = window.location.href;

        if (youtubePattern.test(url))
        {
            return "youtube";
        } else if (netflixPattern.test(url))
        {
            return "netflix";
        } else
        {
            return "unknown";
        }
    }

then a function to generate netflix timestamp and a if statement to differentiate

    function timestampGen(url, time)
    {
        url = url.split('?')[0];
        time = time | 0;
        url = url + '?t=' + time;
        return url;
    }
        if (platform === "youtube")
        {
            current_time = document.querySelector(".video-stream").currentTime.toFixed() || 0;
        } else if (platform === "netflix")
        {
            current_time = timestampGen() || 0;
        } else
        {
            console.error("Unsupported platform");
            return; // Exit the function if the platform is unsupported
        }

        var timestamped_url;

        if (platform === "youtube")
        {
            timestamped_url = "https://youtu.be/" + videoId + "?t=" + current_time;
        } else if (platform === "netflix")
        {
            timestamped_url = "https://www.netflix.com/watch/" + videoId + "?t=" + current_time;
        }

I also changed JSON file to "matches": [ "*://*.youtube.com/watch*", "*://*.netflix.com/watch*" ], but it seems i just keep get the error Uncaught TypeError: Cannot read properties of null (reading 'currentTime')
I feel like this repo should be helpful for generating netflix timestamp but I don’t know how to integrate it.