Header hide when keyboard open only on ios

Hello ,
i have a problem with ionic header
the header is hided when the keyboard opened
in the page i have a title in the header and ion-textarea on the footer .
in other hand the page is a page of chat .
i have the problem only with ios , it works correctly on android.
you find here two photos of the problem
,

this is my ionic info :
Ionic:

Ionic CLI : 5.4.2
Ionic Framework : @ionic/angular 4.10.0
@angular-devkit/build-angular : 0.13.7
@angular-devkit/schematics : 7.2.4
@angular/cli : 7.3.7
@ionic/angular-toolkit : 1.4.1

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 4.1.2, (and 20 other plugins)

Utility:

cordova-res : 0.7.0 (update available: 0.8.0)
native-run : 0.2.8

System:

ios-deploy : 1.9.4
ios-sim : ios-sim/9.0.0-dev.4 darwin-x64 node-v10.16.3
NodeJS : v10.16.3 (/usr/local/bin/node)
npm : 6.9.0
OS : macOS Mojave
Xcode : Xcode 10.2.1 Build version 10E1001

thank you for your help