Dynamic flyouts are not shown when animated

[didster]

Describe the bug
Dynamic flyouts (those added to FlyoutsControl.Items at runtime) dont show with animations enabled (the default). Worked fine prior to around 2.0.0-alpha0872 and I assume related to this commit.

Demo app exhibits same behaviour - all flyouts (which are inlined in xaml) work fine other than dynamic button which doesn't show.

To Reproduce
As per demo code

var flyout = new DynamicFlyout
                      {
                             Header = "Dynamic flyout"
                         };
            // when the flyout is closed, remove it from the hosting FlyoutsControl
            RoutedEventHandler closingFinishedHandler = null;
            closingFinishedHandler = (o, args) =>
                {
                    flyout.ClosingFinished -= closingFinishedHandler;
                    flyoutsControl.Items.Remove(flyout);
                };
            flyout.ClosingFinished += closingFinishedHandler;

            flyoutsControl.Items.Add(flyout);

            flyout.IsOpen = true;

Addition of flyout.AreAnimationsEnabled = false; results in the flyout showing as expected.

Expected behavior
The flyout is shown animated

Environment(please complete the following information):

• MahApps.Metro version [2.0.0-alpha0879]
• OS: Win10 18362
• Visual Studio 2019 (16.5.2)
• .NET Framework: Core 3.1

[punker76]

@didster Thx for using the latest alpha hot stuff and reporting this issue. It's now fixed and will be available with the final v2.0 release.

[didster]

@punker76 Pleasure, just raised another ;-). Thanks for the vast efforts for v2 its coming on great.