When you use El Popper in El table, you can't click OK or cancel to close El Popper. Jsfiddle test can be closed, but not with CLI

### Element UI version
2.15.0

### OS/Browsers version
谷歌,火狐

### Vue version
2.6.12

### Reproduction Link
https://jsfiddle.net/021kjxpL/5/

### Steps to reproduce
jsfiddle测试可以关闭popover, 用cli脚手架后, 点击无法关闭popover, 不知道什么原因

"dependencies": {
"axios": "^0.18.0",
"babel-polyfill": "^6.26.0",
"element-ui": "^2.15.0",
"lodash": "^4.17.20",
"mavon-editor": "^2.6.17",
"vue": "^2.6.10",
"vue-cropperjs": "^3.0.0",
"vue-i18n": "^8.10.0",
"vue-quill-editor": "^3.0.6",
"vue-router": "^3.0.3",
"vue-schart": "^2.0.0",
"vuedraggable": "^2.17.0"
},
"devDependencies": {
"@vue/cli-plugin-babel": "^3.9.0",
"@vue/cli-service": "^3.9.0",
"vue-template-compiler": "^2.6.10"
}

### What is Expected?
使用脚手架,可以点击关闭el-popover

### What is actually happening?
点击后没有反映