Tab icons not visibile on ios

on android both icon and text works fine. but on ios only the selected tab icon is visible.

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Ionic:

ionic (Ionic CLI) : 4.2.1 (/home/galhi/.npm-global/lib/node_modules/ionic)
Ionic Framework : ionic-angular 3.9.2
@ionic/app-scripts : 3.2.0

Cordova:

cordova (Cordova CLI) : 8.0.0
Cordova Platforms : android 7.0.0
Cordova Plugins : cordova-plugin-ionic-keyboard 2.1.2, cordova-plugin-ionic-webview 1.2.1, (and 10 other plugins)

System:

Android SDK Tools : 26.1.1
NodeJS : v8.10.0
npm : 3.5.2
OS : Linux 4.15