[BUG] Invalid cast exception on PlatformAddTags(string[] tags)

[pablolop002]

Describe the bug
App trows InvalidCastException when you call PlatformAddTags function on iOS.

Exception or Stack Trace

Unhandled Exception:
System.InvalidCastException: Specified cast is not valid.
  at Microsoft.Azure.NotificationHubs.Client.NotificationHub.PlatformAddTags (System.String[] tags) [0x00000] in /Users/pablolop002/Projects/Kairos/Microsoft.Azure.NotificationHubs.Client/NotificationHub.ios.cs:119 
  at Microsoft.Azure.NotificationHubs.Client.NotificationHub.AddTags (System.String[] tags) [0x00000] in /Users/pablolop002/Projects/Kairos/Microsoft.Azure.NotificationHubs.Client/NotificationHub.shared.cs:72 
  at kairos_mobile.Views.AppShell..ctor () [0x00087] in /Users/pablolop002/Projects/Kairos/kairos_mobile/Views/AppShell.xaml.cs:42 
  at kairos_mobile.App..ctor () [0x00151] in /Users/pablolop002/Projects/Kairos/kairos_mobile/App.xaml.cs:99 
  at Kairos.iOS.AppDelegate.FinishedLaunching (UIKit.UIApplication app, Foundation.NSDictionary options) [0x00007] in /Users/pablolop002/Projects/Kairos/Kairos.iOS/AppDelegate.cs:28 
  at (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
  at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Library/Frameworks/Xamarin.iOS.framework/Versions/14.8.0.3/src/Xamarin.iOS/UIKit/UIApplication.cs:86 
  at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0000e] in /Library/Frameworks/Xamarin.iOS.framework/Versions/14.8.0.3/src/Xamarin.iOS/UIKit/UIApplication.cs:65 
  at Kairos.iOS.Application.Main (System.String[] args) [0x00001] in /Users/pablolop002/Projects/Kairos/Kairos.iOS/Main.cs:12 
2021-01-20 11:39:55.032 Kairos.iOS[5220:1836293] Unhandled managed exception: Specified cast is not valid. (System.InvalidCastException)
  at Microsoft.Azure.NotificationHubs.Client.NotificationHub.PlatformAddTags (System.String[] tags) [0x00000] in /Users/pablolop002/Projects/Kairos/Microsoft.Azure.NotificationHubs.Client/NotificationHub.ios.cs:119 
  at Microsoft.Azure.NotificationHubs.Client.NotificationHub.AddTags (System.String[] tags) [0x00000] in /Users/pablolop002/Projects/Kairos/Microsoft.Azure.NotificationHubs.Client/NotificationHub.shared.cs:72 
  at kairos_mobile.Views.AppShell..ctor () [0x00087] in /Users/pablolop002/Projects/Kairos/kairos_mobile/Views/AppShell.xaml.cs:42 
  at kairos_mobile.App..ctor () [0x00151] in /Users/pablolop002/Projects/Kairos/kairos_mobile/App.xaml.cs:99 
  at Kairos.iOS.AppDelegate.FinishedLaunching (UIKit.UIApplication app, Foundation.NSDictionary options) [0x00007] in /Users/pablolop002/Projects/Kairos/Kairos.iOS/AppDelegate.cs:28 
  at (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
  at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Library/Frameworks/Xamarin.iOS.framework/Versions/14.8.0.3/src/Xamarin.iOS/UIKit/UIApplication.cs:86 
  at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0000e] in /Library/Frameworks/Xamarin.iOS.framework/Versions/14.8.0.3/src/Xamarin.iOS/UIKit/UIApplication.cs:65 
  at Kairos.iOS.Application.Main (System.String[] args) [0x00001] in /Users/pablolop002/Projects/Kairos/Kairos.iOS/Main.cs:12 

To Reproduce
Call NotificationHub.AddTags from the forms project.

Code Snippet

NotificationHub.NotificationMessageReceived += OnNotificationMessageReceived;
NotificationHub.InstallationSaved += OnInstallationSaved;
NotificationHub.InstallationSaveFailed += OnInstallationSaveFailed;
NotificationHub.Start(Constants.ListenConnectionString, Constants.NotificationHubName);
NotificationHub.AddTags(Constants.Tags);

Expected behavior
Tags added to notification hub.

Screenshots
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Setup (please complete the following information):

• OS: iOS 14.x
• IDE : Visual Studio for Mac 2019
• Cloned repo

Additional context
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