ClipboardRingPopup support for empty ClipboardRing

data/resources/StringResources.resx

@@ -6437,6 +6437,9 @@ Removed the end part of the original message ", reason '${Message}'" since this
   <data name="SharpDevelop.Refactoring.ClipboardRing" xml:space="preserve">
     <value>Clipboard ring</value>
   </data>
+  <data name="SharpDevelop.Refactoring.ClipboardRingEmpty" xml:space="preserve">
+    <value>Clipboard ring is empty</value>
+  </data>
   <data name="SharpDevelop.Refactoring.ClipboardRingCommand" xml:space="preserve">
     <value>From clipboard ring</value>
   </data>

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/ContextActions/ClipboardRing.cs

@@ -34,8 +34,14 @@ namespace ICSharpCode.AvalonEdit.AddIn.ContextActions
 		static ContextActionsPopup MakePopupWithClipboardOptions(EditorRefactoringContext context)
 		{
 			var popupViewModel = new ContextActionsPopupViewModel();
-			popupViewModel.Title = MenuService.ConvertLabel(StringParser.Parse("${res:SharpDevelop.Refactoring.ClipboardRing}"));
-			popupViewModel.Actions = BuildClipboardRingData(context);
+			var actions = BuildClipboardRingData(context);
+			
+			string labelSource = "${res:SharpDevelop.Refactoring.ClipboardRing}";
+			if (actions == null || actions.Count == 0) 
+				labelSource = "${res:SharpDevelop.Refactoring.ClipboardRingEmpty}";
+			
+			popupViewModel.Title = MenuService.ConvertLabel(StringParser.Parse(labelSource));
+			popupViewModel.Actions = actions;
 			return new ClipboardRingPopup { Actions = popupViewModel };
 		}
 		

src/Main/Base/Project/Src/Gui/Components/SideBar/TextEditorSideBar.cs

@@ -83,11 +83,15 @@ namespace ICSharpCode.SharpDevelop.Gui
 		public List<string> GetClipboardRingItems()
 		{
 			var list = new List<string>();
+			if (clipboardRing == null || clipboardRing.Items == null)
+				return list;
+			
 			foreach (var item in clipboardRing.Items) {
 				string itemData = item.Tag as string;
 				if (itemData != null)
 					list.Add(itemData);
 			}
+			
 			return list;
 		}