Show a warning if no gml was found

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

@@ -87,6 +87,8 @@ const regionChooser = (function(){
 		features_by_project = utils.groupBy(features, "project");
 		// Sort CityGMLs inside each project
 		Object.values(features_by_project).forEach(features => features.sort((a, b) => a.name.localeCompare(b.name)));
+
+		return features.length;
 	}
 
 	// The features are not added to a regular vector layer/source,
@@ -404,7 +406,7 @@ const regionChooser = (function(){
 				featureProjection : ol.proj.get('EPSG:3857')
 			});
 		} catch (e){
-			console.error("Couldn't import geometry!");
+			console.warn("Couldn't import geometry!");
 			dataPanel.prepend("<h2 class='error'>Couldn't import geometry!</h2><br/>\n");
 			return false;
 		}
@@ -413,7 +415,7 @@ const regionChooser = (function(){
 		var coordinatesCount = feature.getGeometry().getLinearRing(0).getCoordinates().length - 1;
 
 		if (coordinatesCount < 2){
-			console.error("Too few points!");
+			console.warn("Too few points!");
 			dataPanel.prepend("<h2 class='error'>There should be at least 2 points in WKT polygon</h2><br/>\n");
 			return false;
 		}
@@ -437,8 +439,12 @@ const regionChooser = (function(){
 
 	// Executed by JavaFX when whole page is loaded.
 	publicScope.ready = function() {
-		updateGMLPolygons();
+		var n = updateGMLPolygons();
 		displayHelp();
+		if (n == 0){
+			console.warn("No CityGML found!");
+			dataPanel.prepend("<h2 class='error'>No CityGML has been found!<br/>repository/name.proj/file.gml</h2><br/>\n");
+		}
 		document.documentElement.className = ''; // Stop waiting
 		console.log("Ready!");
 	}