fixed NPE

src/main/java/it/unibz/inf/isochrone/config/ConfigDataset.java

@@ -372,13 +372,13 @@ public class ConfigDataset {
 
 		URL r = null;
 		InputStream r2 = null;
-		Collection<String> resources = null;
+
+		final Collection<String> resources = new ArrayList<>();
 		try {
 			// find resources on disk and add to available ones
 			r = cLoader.getResource("/");
 			if (r != null) {
 				final Collection<File> files = FileUtils.listFiles(new File(r.getFile()), new String[] {DS_CONFIG_EXTENSION}, true);
-				resources = new ArrayList<>(files.size());
 				for (File file : files) {
 					final String filename = file.getName();
 					if (dsConfigPattern.matcher(filename).matches()) {
@@ -388,7 +388,7 @@ public class ConfigDataset {
 			}
 
 			// find resources on classpath (in jar files...) and add to available ones
-			r2 = cLoader.getResourceAsStream("/");
+			r2 = cLoader.getResourceAsStream("");
 			if (r2 != null) {
 				final Collection<String> files = IOUtils.readLines(r2, Charsets.UTF_8);
 				for (String filename : files) {
@@ -406,7 +406,6 @@ public class ConfigDataset {
 				resources.addAll(files);
 			}
 		} catch (IOException e) {
-			resources = null;
 			LOGGER.warn("Datasets could not be read. There might be no configured datasets available!");
 		} finally {
 			if (r2 != null) {
@@ -418,7 +417,7 @@ public class ConfigDataset {
 			}
 		}
 
-		if (resources == null || resources.size() <= 0) {
+		if (resources.size() <= 0) {
 			LOGGER.debug(" - no datasets available");
 			return Collections.emptyList();
 		}