Put this in the chrome dev tools under Sources -> Snippets. Use when your referee's setUpLevel code prevents loading your level in the editor. It'll add "{}" to the end of your referee's extraCode, which you can remove after you've fixed it.

CoCoDisableRef.js

(function(currentView) {
    var thangs = currentView.level.get('thangs');
    var refereeThang = null;
    for(var i=0; i < thangs.length; i++) {
        var thang = thangs[i];
        if(thang.components) {
            for(var j=0; j < thang.components.length; j++) {
                var component = thang.components[j];
                if(component.config && component.config.extraCode) {
                    refereeThang = thang;
                    refereeCode = component.config.extraCode;
                    component.config.extraCode = refereeCode + '\n{}';
                    console.log('Found referee, commenting out extraCode');
                    currentView.level.set('thangs',thangs);
                    break;
                }
            }
        }
        if(refereeThang !== null) { 
            break;
        }
    }
    if(refereeThang === null) {
        console.log("Referee not found.");
    }
})(currentView);

If you can't load the level at all due to an infinite loop in setUpLevel, then you can get to the thangs from any other page on codecombat.com like this:

var thangs = JSON.parse(localStorage["lscache-" + currentView.level.id]).thangs

You could then adapt this script to JSON.stringify() the updated level and put it in localStorage with that cache key.

Using Safari's Web Inspector the following HTML can be injected into the broken page. Creating an easy click button to run the above code. This should work on Firefox as well.

<button onclick="var t = currentView.level.get('thangs');var r = null;for(var i=0; i < t.length; i++) {var h = t[i];if(h.components) {for(var j=0; j < h.components.length; j++) {var c = h.components[j];if(c.config && c.config.extraCode) {r = h;var e = c.config.extraCode;c.config.extraCode = e + '\n{}';console.log('Found referee, commenting out extraCode');currentView.level.set('thangs',t);break;}}}if(r !== null) {break;}}if(r === null) {console.log('Referee not found.');}">Click to Fix the referee Code</button><p>Then refresh the browser page</p>