Add empty for hotkey model

Author: Jack251970

Flow.Launcher.Infrastructure/Hotkey/HotkeyModel.cs

@@ -51,6 +51,8 @@ public ModifierKeys ModifierKeys
 
         public readonly bool IsEmpty => CharKey == Key.None && !Alt && !Shift && !Win && !Ctrl;
 
+        public static HotkeyModel Empty => new();
+
         public HotkeyModel(string hotkeyString)
         {
             Parse(hotkeyString);