error data binding fix

VECTO3GUI/ViewModel/Impl/XMLViewModel.cs

@@ -4,6 +4,7 @@ using System.IO;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
+using System.Windows.Input;
 using ICSharpCode.AvalonEdit.Highlighting;
 using ICSharpCode.AvalonEdit.Utils;
 
@@ -75,5 +76,10 @@ namespace VECTO3GUI.ViewModel.Impl
 				TextContent =  FileReader.ReadFileContent(fileStream, Encoding.UTF8);
 			}
 		}
+
+		public ICommand CloseWindowCommand
+		{
+			get { return null; }
+		}
 	}
 }