TypeError: Cannot read property 'toUpperCase' of undefined.... but it works in JSFiddle?

Hi guys, I'm creating a site in Node.JS and one of the things I'm attempting to do is compare a search input string with a CSV file which is acting as my database.

I'm trying to remove the case sensitivity as you can see below:

function matchData(searchData){
    var fileContent = [];
    var results = new Array();
    fileContent = fs.readFileSync('./data/database.csv', 'utf8').split('\n');

    for(var line of fileContent){
        var result = line.split(',');

        var check = result[5].toUpperCase();
        console.log(check);
        var test = searchData.toUpperCase();
        console.log(test);

        if(check === test)
        {
            results.push(result);
        }
    }
    return results;
}

The crazy thing is, the console.log(check) and console.log(test) both spit out the uppercase strings so it should work, but every time I run it I get "TypeError: Cannot read property 'toUpperCase' of undefined". I tried toLowerCase() instead and it did exactly the same thing.

And if I type the string in case sensitive, I know the function works perfectly.

Can anyone tell me what I'm doing wrong?