Behavior if no icon is found for cluster.

[donquixote]

Clusterer.PopUp = function(cluster){    
    var clusterer = cluster.clusterer;    
    var html = '<table width="300">';
    var n = 0;
    for (var i = 0; i < cluster.markers.length; ++i){
        var marker = cluster.markers[i];
        if (marker != null){
            ++n;
            var icon_marker = marker.getIcon();
            html += '<tr><td>';
            html += '<img src="' + icon_marker.url + '" width="' + (icon_marker.size.width / 2) + '" height="' + (icon_marker.size.height / 2) + '">';

If marker.getIcon() returns undefined, the method will blow up like this:

Uncaught TypeError: Cannot read property 'url' of undefined

This method fires a cluster is being clicked.

See also Clusterer2.js: marker.getIcon() returns null, and Clusterer.PopUp() blows up. in the drupal.org GMap issue queue.
I expect this is not an either-or, but both the Drupal module and the clusterer should add some sanity checks for early problem detection.

Btw, I remember having used the clusterer successfully in past projects, and having been happy with it. So something must have changed in the clusterer or in the Drupal module, or my setup is not correct. But even if my setup is not correct, adding some sanity checks can't be wrong.

Thanks!

[donquixote]

Ok, this turned out to be a configuration issue. Somehow there was no marker configured.
But I still think this should be detected earlier with a meaningful message.