WPF layout bug

wpflayoutbug.cs

<Window
    x:Class="WpfApp1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow"
    Width="800"
    Height="450"
    SizeToContent="WidthAndHeight">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition />
        </Grid.RowDefinitions>
        <TextBox
            Grid.Row="1"
            Grid.Column="1"
            Text="hello world" />
    </Grid>
</Window>

compile and run, then click on the window border, and observe the layout changes.