Fix InvalidCastException in ShowErrorHelpCommand.Run() - revert owner of ErrorContextMenu to errorView instead of the pad.

src/Main/Base/Project/Src/Gui/Pads/ErrorList/ErrorListPad.cs

@@ -120,7 +120,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 			errorView.ItemsSource = errors;
 			errorView.MouseDoubleClick += ErrorViewMouseDoubleClick;
 			errorView.Style = (Style)new TaskViewResources()["TaskListView"];
-			errorView.ContextMenu = MenuService.CreateContextMenu(this, DefaultContextMenuAddInTreeEntry);
+			errorView.ContextMenu = MenuService.CreateContextMenu(errorView, DefaultContextMenuAddInTreeEntry);
 			
 			errorView.CommandBindings.Add(new CommandBinding(ApplicationCommands.Copy, ExecuteCopy, CanExecuteCopy));
 			errorView.CommandBindings.Add(new CommandBinding(ApplicationCommands.SelectAll, ExecuteSelectAll, CanExecuteSelectAll));

src/Main/Base/Project/Src/Gui/Pads/TaskList/TaskListPadCommands.cs

@@ -54,15 +54,13 @@ namespace ICSharpCode.SharpDevelop.Gui
 			this.token = token;
 			this.Content = token;
 			this.Command = this;
-			this.CommandParameter = TaskListPad.Instance;
 			this.IsChecked = TaskListPad.Instance.DisplayedTokens[token];
 			SetResourceReference(FrameworkElement.StyleProperty, ToolBar.CheckBoxStyleKey);
 		}
 		
 		bool ICheckableMenuCommand.IsChecked(object parameter)
 		{
-			var pad = (TaskListPad)parameter;
-			return pad.DisplayedTokens[token];
+			return TaskListPad.Instance.DisplayedTokens[token];
 		}
 		
 		public bool CanExecute(object parameter)
@@ -72,7 +70,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 		
 		public void Execute(object parameter)
 		{
-			var pad = (TaskListPad)parameter;
+			var pad = TaskListPad.Instance;
 			pad.DisplayedTokens[token] = IsChecked == true;
 			if (pad.IsInitialized)
 				pad.UpdateItems();