[v4 - iOS] ion-tab-bar reappearing when switching input focus

Bug Report

Ionic version: [x] 4.x

Current behavior: When using Tabs together with a tab bar, the tab bar properly hides when the keyboard openes for input. When switching to another input element while the keyboard is still open, the tab bar appears on top the the keyboard

Expected behavior: The tab bar should stay hidden as long as the keyboard is open.

Steps to reproduce:

1. Use the starter app with the latest WkWebView Plugin (3.x) - add multiple inputs (text) to a page.
2. Build for iOS and run on iOS
3. Select any input --> keyboardWillShow and keyboardDidShow will be properly triggered, the keyboard appears, and the tab bar disappears.
4. With the keyboard being still open, select another input (field). --> triggers keyboardWillHide and keyboardDidHide and does not trigger the show and didShow events, thus letting the tab bar reappear on top of the keyboard (and messing around with view height calculations).

Other information: As v3 and v4-beta did not automatically hide the tabs, we worked around this issue by hiding the bar manually (by listening to the Keyboard plugin events first). With v4-stable this seems to be done by the tabs itself - but it also seems to be partially broken

Ionic info:

Ionic:

   ionic (Ionic CLI)             : 4.10.2 (/usr/local/lib/node_modules/ionic)
   Ionic Framework               : @ionic/angular 4.0.1
   @angular-devkit/build-angular : 0.12.4
   @angular-devkit/schematics    : 7.2.4
   @angular/cli                  : 7.2.4
   @ionic/angular-toolkit        : 1.3.0

Cordova:

   cordova (Cordova CLI) : 8.0.0
   Cordova Platforms     : ios 4.5.5
   Cordova Plugins       : cordova-plugin-ionic-keyboard 2.1.3, cordova-plugin-ionic-webview 3.1.2, (and 4 other plugins)

System:

   Android SDK Tools : 25.2.2 (/Users/xxx/Library/Android/sdk)
   NodeJS            : v8.12.0 (/usr/local/bin/node)
   npm               : 6.4.1
   OS                : macOS Mojave
   Xcode             : Xcode 10.1 Build version 10B61

[wilk-polarny]

Update: This issue is still present in 4.2.0 and is a blocker for our app release after migrating to v4.

[ionitron-bot[bot]]

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