My goal is to provide a field on the Account that lists all the products that have been sold from the various Opportunities.  I am looking for the best solution to achieve the goal.

I've tried a second time using a brand new Trailhead Playground, and still get the error when checking the challenge:
"Challenge Not yet complete... here's what's wrong: 
There was an unexpected error while verifying this challenge. Usually this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: VRHJDGJD "

I'm passing this challenge, however when I actually test it out by clicking on an account in the account list item, I get this exception: 

"Something has gone wrong. Action failed: c$AccountMap$controller$accountSelected [TypeError: Cannot read property 'reuseTiles' of undefined] Failing descriptor: {c$AccountMap$controller$accountSelected}."

I did some debugging and found that the location and latitude of the account are indeed being capture by my event, so it looks like this might be a problem with the leaflet function map.panTo(). Does anyone know the solution to this issue? Here's my code, although it's exactly the same as the tutorial's.
 

({
    jsLoaded: function(component, event, helper) {

        setTimeout(function() {
            var map = L.map('map', {zoomControl: false}).setView([37.784173, -122.401557], 14);
            L.tileLayer('https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/{z}/{y}/{x}',
                {
                    attribution: 'Tiles © Esri'
                }).addTo(map);
            component.set("v.map", map);
        });
    },

    accountsLoaded: function(component, event, helper) {

        // Add markers
        var map = component.get('v.map');
        var accounts = event.getParam('accounts');
        for (var i=0; i<accounts.length; i++) {
            var account = accounts[i];
            var latLng = [account.Location__Latitude__s, account.Location__Longitude__s];
            L.marker(latLng, {account: account}).addTo(map);
        }  
    },

    accountSelected: function(component, event, helper) {
        // Center the map on the account selected in the list
        var map = component.get('v.map');
        var account = event.getParam("account");
        alert(account.Location__Latitude__s + ', ' + account.Location__Longitude__s);
        map.panTo([account.Location__Latitude__s, account.Location__Longitude__s]);
    }
})