Commented Issue: AvalonDock : Height (and Width) of the LayoutAnchorableFloatingWindow is too small [22457]

Hi,

Go in file Xceed.Wpf.AvalonDock.DockingManager.cs,
in method "StartDraggingFloatingWindowForPane"
and replace :
```
if( fwWidth == 0.0 )
fwWidth = paneAsWithActualSize.ActualWidth;
if( fwHeight == 0.0 )
fwHeight = paneAsWithActualSize.ActualHeight;
```
with
if( fwWidth == 0.0 )
fwWidth = paneAsWithActualSize.ActualWidth + 10; //10 includes BorderThickness and Margins inside LayoutAnchorableFloatingWindowControl.
if( fwHeight == 0.0 )
fwHeight = paneAsWithActualSize.ActualHeight + 10; //10 includes BorderThickness and Margins inside LayoutAnchorableFloatingWindowControl.

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