fix SD-1738 - Ctrl+Shift+Tab does not work in active files dialog

src/Libraries/AvalonDock/AvalonDock/DockingManager.cs

@@ -1054,7 +1054,7 @@ namespace AvalonDock
         
         protected override void OnKeyDown(KeyEventArgs e)
         {
-            bool isCtrlDown = Keyboard.Modifiers == ModifierKeys.Control;
+            bool isCtrlDown = Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl);
             bool _navigatorWindowIsVisible = navigatorWindow != null ? navigatorWindow.IsVisible : false;
             Debug.WriteLine(string.Format("OnKeyDn {0} CtrlDn={1}", e.Key, isCtrlDown));
 
@@ -1078,7 +1078,7 @@ namespace AvalonDock
 
         protected override void OnKeyUp(KeyEventArgs e)
         {
-            bool isCtrlDown = Keyboard.Modifiers == ModifierKeys.Control;
+        	 bool isCtrlDown = Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl);
             bool _navigatorWindowIsVisible = navigatorWindow != null ? navigatorWindow.IsVisible : false;
             Debug.WriteLine(string.Format("OnKeyUp {0} CtrlDn={1}", e.Key, isCtrlDown));
 
@@ -1087,6 +1087,7 @@ namespace AvalonDock
                 if (!_navigatorWindowIsVisible && e.Key == Key.Tab)
                 {
                     ShowNavigatorWindow();
+                    _navigatorWindowIsVisible = true;
                 }
 
                 if (_navigatorWindowIsVisible)

src/Libraries/AvalonDock/AvalonDock/NavigatorWindow.cs

@@ -196,6 +196,9 @@ namespace AvalonDock
         {
             if (key == Key.Tab)
             {
+            	if (Keyboard.IsKeyDown(Key.LeftShift) || Keyboard.IsKeyDown(Key.RightShift))
+            		 MoveToPreviousContent();
+            	 else
                	 MoveToNextContent();
                 return true;
             }

src/Main/Base/Project/Src/Commands/WindowCommands.cs

@@ -11,7 +11,8 @@ namespace ICSharpCode.SharpDevelop.Commands
 	{
 		public override void Run()
 		{
-			if (WorkbenchSingleton.Workbench.ActiveWorkbenchWindow == null) {
+			if (WorkbenchSingleton.Workbench.ActiveWorkbenchWindow == null ||
+			   		WorkbenchSingleton.Workbench.WorkbenchWindowCollection.Count == 0) {
 				return;
 			}
 			int index = WorkbenchSingleton.Workbench.WorkbenchWindowCollection.IndexOf(WorkbenchSingleton.Workbench.ActiveWorkbenchWindow);
@@ -23,7 +24,8 @@ namespace ICSharpCode.SharpDevelop.Commands
 	{
 		public override void Run()
 		{
-			if (WorkbenchSingleton.Workbench.ActiveWorkbenchWindow == null) {
+			if (WorkbenchSingleton.Workbench.ActiveWorkbenchWindow == null ||
+					WorkbenchSingleton.Workbench.WorkbenchWindowCollection.Count == 0) {
 				return;
 			}
 			int index = WorkbenchSingleton.Workbench.WorkbenchWindowCollection.IndexOf(WorkbenchSingleton.Workbench.ActiveWorkbenchWindow);