fix bugs

core/src/main/java/asys/core/ASysCore.java

@@ -40,6 +40,7 @@ class ASysCore implements ICore {
 
         File libsDir = new File(directory);
         String[] jarsList = libsDir.list();
+        if (jarsList != null) {
             for (String jar : jarsList) {
                 if (!jar.endsWith(".jar")) continue;
                 try {
@@ -50,6 +51,7 @@ class ASysCore implements ICore {
                     logger.error(String.format("Error load jar \"%s/%s\"", directory, jar), e);
                 }
             }
+        }
 
         return bundlesList;
     }