#vulnerable code 
                                private static void save(MethodNode methodNode) {
        try {
            MethodNodeService methodNodeService = ApplicationContextHelper.popBean(MethodNodeService.class);
            methodNodeService.saveNotRedo(methodNode);
        } catch (Exception e) {
            logger.error("methodNodeService保存方法节点失败");
            e.printStackTrace();
        }
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private static void save(MethodNode methodNode) {
        try {
            MethodNodeService methodNodeService = ApplicationContextHelper.popBean(MethodNodeService.class);
            assert methodNodeService != null;
            methodNodeService.saveNotRedo(methodNode);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }