fixed issue: no optimpref file existing

Author: christoph

TimeNETOptimizationEnvironment/src/toe/optimization/OptimizerPreferences.java

@@ -1345,19 +1345,21 @@ public int getNumberOfOptiPrefs() {
 
         File[] listOfFiles = folderToScan.listFiles();
 
-        for (int i = 0; i < listOfFiles.length; i++) {
-            if (listOfFiles[i].isFile()) {
-                target_file = listOfFiles[i].getName();
-                if (target_file.startsWith(standardFile.getName())) {
-                    numberOfFoundOptiPrefs++;
+        if (listOfFiles  != null) {
+            for (int i = 0; i < listOfFiles.length; i++) {
+                if (listOfFiles[i].isFile()) {
+                    target_file = listOfFiles[i].getName();
+                    if (target_file.startsWith(standardFile.getName())) {
+                        numberOfFoundOptiPrefs++;
+                    }
                 }
             }
         }
         return numberOfFoundOptiPrefs;
     }
 
     /**
-     * Updates the label to shwo how many Optipreferences are stored in
+     * Updates the label to show how many Optipreferences are stored in
      * pref-folder
      */
     private void updateNumberOfOptiPrefs() {