Settings migration - config directory may not be created yet, at least on Linux

Author: jisedlac

visualvm/startup/src/org/graalvm/visualvm/modules/startup/ImportSettings.java

@@ -243,9 +243,9 @@ private static void cleanupUserdir(File userdir, File[] initialFiles) {
             for (File f : imported) delete(f);
         }
 
-        // Cleanup config directory (created but empty before the import)
+        // Cleanup config directory (may be created but empty before the import)
         File config = new File(userdir, "config");                              // NOI18N
-        for (File f : config.listFiles()) delete(f);
+        if (config.isDirectory()) for (File f : config.listFiles()) delete(f);
     }
 
     private static void delete(File file) {