Fixed process executing on clicking enter if no text in search box

src/modules/launcher/Wox/ViewModel/MainViewModel.cs

@@ -152,6 +152,8 @@ namespace Wox.ViewModel
                     results.SelectedIndex = int.Parse(index.ToString());
                 }
 
+                if(results.SelectedItem != null)
+                {
                     //If there is a context button selected fire the action for that button before the main command. 
                     bool didExecuteContextButton = results.SelectedItem?.ExecuteSelectedContextButton() ?? false;
 
@@ -181,6 +183,7 @@ namespace Wox.ViewModel
                             }
                         }
                     }
+                }              
             });
 
             LoadContextMenuCommand = new RelayCommand(_ =>
@@ -419,6 +422,7 @@ namespace Wox.ViewModel
             }
             else
             {
+                Results.SelectedItem = null;
                 Results.Clear();                
                 Results.Visbility = Visibility.Collapsed;
             }

src/modules/launcher/Wox/ViewModel/ResultsViewModel.cs

@@ -65,6 +65,10 @@ namespace Wox.ViewModel
                     _selectedItem = value;
                     _selectedItem.ActivateContextButtons(ResultViewModel.ActivationType.Selection);
                 }
+                else
+                {
+                    _selectedItem = value;
+                }
             }
         }