Describe the bug
The SpaceExtension causes error

'' is not a valid value for the 'System.Windows.Controls.Control.Padding' property on a Setter.

and make the WPF designer stopped working.

Reproduce

It's just randomly appear in designer. like this.

Additional context
I've resolved some of error this by adding this piece of code in App.xaml.cs:

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);
    AdonisUI.SpaceExtension.SetSpace(8, 8);
}

but still, it's not the solution right?

Is there any Fallback value for the SpaceExtension if something's not right?