例外が発生しました: Object reference not set to an instance of an object

System.NullReferenceException: Object reference not set to an instance of an object
  at MonoDevelop.Core.Gui.Dialogs.TreeViewOptions..ctor (Gtk.Window parentWindow, IProperties properties, IAddInTreeNode node) [0x00000] 
  at MonoDevelop.Projects.Gui.Dialogs.CombineOptionsDialog..ctor (Gtk.Window parentWindow, MonoDevelop.Projects.Combine combine, IAddInTreeNode node, IAddInTreeNode configurationNode) [0x00000] 
  at MonoDevelop.Ide.Gui.ProjectOperations.ShowOptions (MonoDevelop.Projects.CombineEntry entry, System.String panelId) [0x00000] 
  at MonoDevelop.Ide.Commands.ConfigureDeployTargetsHandler.Run () [0x00000] 
  at MonoDevelop.Components.Commands.CommandHandler.Run (System.Object dataItem) [0x00000] 
  at MonoDevelop.Components.Commands.ActionCommand.DispatchCommand (System.Object dataItem) [0x00000] 
  at MonoDevelop.Components.Commands.CommandManager.DispatchCommand (System.Object commandId, System.Object dataItem, System.Object initialTarget) [0x00000]