Adding a empty layer as the guide layer leads to errors

[sidney-pauly]

var guideLayer = new L.LayerGroup()
var marker = new L.Marker(...)

marker.snapediting = new L.Handler.MarkerSnap(map, marker);
marker.snapediting.addGuideLayer(guideLayer);
marker.snapediting.enable();

If the guide is just a empty layer just like in this example above and you start moving the marker an error is thrown in L.Handler.MarkerSnap in the _snapMarker function. This is because no snap target is found but one is expected in this function. I propose to just add a condition like this into the function:

_snapMarker: function(e) {
        var closest = L.Snap.snapMarker(e, this._guides, this._map, this.options, this._buffer);
        

        if (closest && e.originalEvent && e.originalEvent.clientX && closest.layer && closest.latlng) 
     //       ^
     //       |
     //     Add this
{
            var snapTouchPoint = this._map.project(closest.latlng, this._map.getZoom());
            e.originalEvent.clientX = snapTouchPoint.x;
            e.originalEvent.clientY = snapTouchPoint.y;
            e.originalEvent.snapped = true;
        }
    }