Created Unassigned: LayoutAnchorable doesn't resize correctly if below a LayoutDocumentPane [22243]

If you have a LayoutAnchorable below a LayoutDocumentPane and you resize the document to its minimum height, then the LayoutAnchorable doesn't resize correctly if you resize the height of the window.

For a sample please see my code below:

```
<Window x:Class="AvalonTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:ad="http://schemas.xceed.com/wpf/xaml/avalondock"
xmlns:local="clr-namespace:AvalonTest"
mc:Ignorable="d"
Title="MainWindow" Height="600" Width="800">
<Grid>
<ad:DockingManager>
<ad:LayoutRoot>
<ad:LayoutPanel Orientation="Vertical">
<ad:LayoutDocumentPane>
<ad:LayoutDocument>
<Button>
First move splitter up. Then Resize the height of the window.
</Button>
</ad:LayoutDocument>
</ad:LayoutDocumentPane>
<ad:LayoutAnchorablePane>
<ad:LayoutAnchorable>
<Button>
Lower part of this anchorable disappeares.
</Button>
</ad:LayoutAnchorable>
</ad:LayoutAnchorablePane>
</ad:LayoutPanel>
</ad:LayoutRoot>
</ad:DockingManager>
</Grid>
</Window>

```