iOS13适配

一、UITabbar的黑线问题，额外增加如下代码

    UITabBar * tabbar = self.tabBarController.tabBar;

    if(@available(iOS13.0, *)) {

        UITabBarAppearance * tabbarAppearance = [tabbar standardAppearance];

        tabbarAppearance.shadowColor= [UIColor clearColor];

        tabbar.standardAppearance = tabbarAppearance;

    }