报错如下，需要怎么解决：
main.js:15 [Vue warn]: Failed to resolve component: el-submenu
at <SidebarItem key="/user/center" route= {path: ‘/user/center’, name: ‘userCenter’, meta: {…}, children: Array(0), component: ƒ}children: []component: () => {…}meta: {title: ‘userCenter’, icon: ‘el-icon-user’}name: “userCenter"path: “/user/center”[[Prototype]]: Object >
at <BaseTransition mode=“out-in” onBeforeEnter=fn onEnter=fn … >
at <Transition mode=“out-in” onBeforeEnter=fn onEnter=fn … >
at
at <ElMenu uniqueOpened=true background-color=”#545c64" text-color="#fff" … >
at
at
at <Index class=“sidebar-container” style= {backgroundColor: ‘#304156’} >
at <Index onVnodeUnmounted=fn ref=Ref< undefined > >
at
at