correct bug for when there are no engines installed

src/main/java/org/bioimageanalysis/icy/deeplearning/versionmanager/downloading/DeepLearningVersionDownloader.java

@@ -100,6 +100,8 @@ public class DeepLearningVersionDownloader
      * @return string array with folder names inside the engines folder
      */
     public static String[] getEnginePaths() {
+    	if (!downloadsPath.toFile().exists())
+    		return new String[0];
     	return downloadsPath.toFile().list();
     }
 

src/main/java/org/bioimageanalysis/icy/deeplearning/versionmanager/version/AvailableDeepLearningVersions.java

@@ -151,6 +151,8 @@ public class AvailableDeepLearningVersions
      */
     public static List<DeepLearningVersion> loadDownloaded()
     {
+    	if (DeepLearningVersionDownloader.getEnginePaths().length == 0)
+    		return new ArrayList<DeepLearningVersion>();
     	List<DeepLearningVersion> versions = Arrays.stream(DeepLearningVersionDownloader.getEnginePaths())
     			.map(t -> {
 					try {