Fix crash iOS AppDelegate OnActivated

[fedemkr]

Type of change

• Bug fix
• New feature development
• Tech debt (refactoring, code cleanup, dependency upgrades, etc)
• Build/deploy pipeline (DevOps)
• Other

Objective

Fix crash happened on AppDelegate -> OnActivated

Code changes

• AppDelegate: Added null check on OnActivated for the KeyWindow and also made a const for the tag of the splash view.

Testing requirements

The flow for the crash to happen is unknown but at least we should check that the splash shown when "minimizing" the app should be displayed correctly and hide correctly when going back to the application.

Before you submit

• I have added unit tests where it makes sense to do so (encouraged but not required)
• This change requires a documentation update (notify the documentation team)
• This change has particular deployment requirements (notify the DevOps team)