Only zoom extent when a feature is added.

src/main/resources/eu/simstadt/regionchooser/website/script/simstadt_openlayers.js

@@ -85,7 +85,7 @@ var regionChooser = (function(){
 	var geoJsonFormat = new ol.format.GeoJSON();
 	var kmlFormat = new ol.format.KML({extractStyles: false});
 
-	kml_layer.addEventListener("change", function() {
+	kml_source.addEventListener("addfeature", function() {
 		map.getView().fitExtent(kml_source.getExtent(), (map.getSize()));
 	});