No output file selected.

src/main/java/eu/simstadt/regionchooser/RegionChooserBrowser.java

@@ -87,6 +87,10 @@ public int downloadRegionFromCityGMLs(String wktPolygon, String project, String
 			File outputFile = selectSaveFileWithDialog(project,
 					csvCitygmls.replace(";", "_").replace(".gml", ""), "selected_region");
 
+			if (outputFile == null) {
+				return -1;
+			}
+
 			int count;
 			try (BufferedWriter gmlWriter = Files.newBufferedWriter(outputFile.toPath())) {
 				count = RegionExtractor.selectRegionDirectlyFromCityGML(wktPolygon, srsName, gmlWriter, paths);

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

@@ -244,7 +244,11 @@ var regionChooser = (function(){
 				console.log("Selected region is written in " + srsName + " coordinate system.");
 				try {
 					var count = fxapp.downloadRegionFromCityGMLs(sketchAsWKT(srsName), project, citygmlNames.join(";"), srsName);
-					dataPanel.prepend("<h2 class='ok'>Done! (" + count + " buildings found) </h2><br/>\n");
+					if (count == -1){
+						console.log("No output file has been selected.");
+					} else {
+						dataPanel.prepend("<h2 class='ok'>Done! (" + count + " buildings found) </h2><br/>\n");
+					}
 				} catch (e) {
 					console.warn("ERROR : " + e);
 					dataPanel.prepend("<h2 class='error'>Some problem occured!</h2><br/>\n");