fix SD-1774 - Floating and AutoHide windows are reset to Docked state when BringPadToFront() is called (http://bugtracker.sharpdevelop.net/issue/ViewIssue.aspx?id=1774&PROJID=4)

src/Main/Base/Project/Src/Gui/Workbench/Layouts/AvalonDockLayout.cs

@@ -222,7 +222,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 		{
 			AvalonPadContent p;
 			if (pads.TryGetValue(padDescriptor, out p))
-				return p.IsVisible;
+				return p.State != DockableContentState.Hidden;
 			else
 				return false;
 		}