fix typing

Author: Carreau

src/prompt_toolkit/input/kitty_keyboard.py

@@ -291,7 +291,7 @@ def _apply_modifiers(base: Keys, ctrl: bool, shift: bool) -> Keys:
     # emulate that here; Shift+Fn just returns Fn for now.
     if base.value.startswith("f") and base.value[1:].isdigit():
         if ctrl:
-            ctrl_key = getattr(Keys, "Control" + base.name, None)
+            ctrl_key: Keys | None = getattr(Keys, "Control" + base.name, None)
             if ctrl_key is not None:
                 return ctrl_key
         return base