我正在处理一个ionic 3项目，当尝试运行“ cordova platform add ios”时，出现以下错误：
Using cordova-fetch for cordova-ios@~4.5.4
Adding ios project...
Creating Cordova project for the iOS platform:
Path: platforms/ios
Package: io.ionic.starter
Name: MyApp
iOS project created with cordova-ios@4.5.5
Installing "cordova-plugin-device" for ios
Installing "cordova-plugin-ionic-keyboard" for ios
Installing "cordova-plugin-ionic-webview" for ios
Failed to install 'cordova-plugin-ionic-webview': TypeError: Invalid Version: undefined
at new SemVer (/usr/local/lib/node_modules/cordova/node_modules/semver/semver.js:305:11)
at Range.test (/usr/local/lib/node_modules/cordova/node_modules/semver/semver.js:1112:15)
at Function.satisfies (/usr/local/lib/node_modules/cordova/node_modules/semver/semver.js:1161:16)
at checkEngines (/usr/local/lib/node_modules/cordova/node_modules/cordova-lib/src/plugman/install.js:116:20)
at /usr/local/lib/node_modules/cordova/node_modules/cordova-lib/src/plugman/install.js:313:16
at _fulfilled (/usr/local/lib/node_modules/cordova/node_modules/q/q.js:854:54)
at /usr/local/lib/node_modules/cordova/node_modules/q/q.js:883:30
at Promise.promise.promiseDispatch (/usr/local/lib/node_modules/cordova/node_modules/q/q.js:816:13)
at /usr/local/lib/node_modules/cordova/node_modules/q/q.js:624:44
at runSingle (/usr/local/lib/node_modules/cordova/node_modules/q/q.js:137:13)
Invalid Version: undefined
离子信息：
Ionic:
ionic (Ionic CLI) : 4.3.1 (/usr/local/lib/node_modules/ionic)
Ionic Framework : ionic-angular 3.9.2
@ionic/app-scripts : 3.2.0
Cordova:
cordova (Cordova CLI) : 8.1.2 (cordova-lib@8.1.1)
Cordova Platforms : ios 4.5.5
Cordova Plugins : cordova-plugin-ionic-keyboard 2.1.3, cordova-plugin-ionic-webview 2.2.3, (and 4 other plugins)
System:
Android SDK Tools : 26.1.1 (/Users/voxiel/Library/Android/sdk/)
ios-deploy : 1.9.4
NodeJS : v10.4.1 (/usr/local/Cellar/node/10.4.1/bin/node)
npm : 6.1.0
OS : macOS High Sierra
Xcode : Xcode 9.4.1 Build version 9F2000
感谢您的帮助！