#fixed code
                                public void addScript(Script script) {
        ScriptEngine engine = manager.getEngineByName(script.getLanguage());
        if (engine == null) {
            logger.error("No ScriptEngine found for language " + script.getLanguage() + ". Available languages are: " +
                languages);
            return;
        }
        if (engine.getFactory().getParameter("THREADING") == null) {
            scripts.put(script.getName(), new ThreadLocalScriptRunner(script));
        } else {
            scripts.put(script.getName(), new MainScriptRunner(engine, script));
        }
    }
#vulnerable code 
                                public void addScript(Script script) {
        ScriptEngine engine = manager.getEngineByName(script.getLanguage());
        if (engine == null) {
            logger.error("No ScriptEngine found for language " + script.getLanguage());
        }
        if (engine.getFactory().getParameter("THREADING") == null) {
            scripts.put(script.getName(), new ThreadLocalScriptRunner(script));
        } else {
            scripts.put(script.getName(), new MainScriptRunner(engine, script));
        }
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE