fix #13599 A warning dialog pops up when trying to switch the values for the FormScreenCaptureMode property

[Epica3055]

Fixes #13599

Root Cause

At design time TopLevel is false

    public ScreenCaptureMode FormScreenCaptureMode
    {
        get => Properties.GetValueOrDefault(s_propFormScreenCaptureMode, ScreenCaptureMode.Allow);
        set
        {
            if (FormScreenCaptureMode == value)
            {
                return;
            }

            if (!TopLevel)
            {
                throw new InvalidOperationException(SR.FormScreenCaptureModeRequiresTopLevel);
            }

            SourceGenerated.EnumValidator.Validate(value);
            Properties.AddOrRemoveValue(s_propFormScreenCaptureMode, value);

            if (IsHandleCreated)
            {
                SetScreenCaptureModeInternal(value);
            }
        }
    }

Proposed changes

• Add another condition to check if the control is in design mode

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 76.69604%. Comparing base (08485db) to head (f30cfaa).
Report is 17 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #13662         +/-   ##
===================================================
+ Coverage   76.60828%   76.69604%   +0.08776%     
===================================================
  Files           3253        3255          +2     
  Lines         640996      641599        +603     
  Branches       47439       47490         +51     
===================================================
+ Hits          491056      492081       +1025     
+ Misses        146290      145863        -427     
- Partials        3650        3655          +5     

Flag	Coverage Δ
Debug	76.69604% <0.00000%> (+0.08776%)	⬆️
integration	18.99105% <0.00000%> (-0.00279%)	⬇️
production	51.21705% <0.00000%> (+0.14804%)	⬆️
test	97.41503% <ø> (+0.00328%)	⬆️
unit	48.59564% <0.00000%> (+0.14874%)	⬆️

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[KlausLoeffelmann]

Works for now for this as a quick workaround.
But we need to address the version issue for different .NET Server versions, anyway.