Using iOS front camera causes crash when closing the page

[gwest]

When using the front camera in iOS, closing the form will cause an application crash with the following stack trace:

Foundation.MonoTouchException Message=Objective-C exception thrown. Name: NSInvalidArgumentException Reason: *** -[AVCaptureDevice setFocusMode:] Unsupported focusMode - use -isFocusModeSupported: to discover valid focus modes

To reproduce the error on the latest master commit (f8abca8) I did the following

1. In Sample.Forms.HomePage.cs, add code to make the "Scan with Default Overlay" use the front camera on line 31
   new ZXing.Mobile.MobileBarcodeScanningOptions { UseFrontCameraIfAvailable = true }
2. Click the "Scan with Default Overlay" button to open the scanner.
3. Click the "< ZXing.Net.Mobile" back button to close the scanner.

I've attached the full error in case it helps: Foundation.MonoTouchException.txt.

Tested with iPad (8th generation) on iOS 14.4

[simader]

please merge....

Please merge

[AntonKurasov]

We have the same issue but with the rear camera. Any updates on the merge request?