fix types (strange mypy bug)

Author: Carreau

src/prompt_toolkit/input/kitty_keyboard.py

@@ -275,13 +275,13 @@ def _apply_modifiers(base: Keys, ctrl: bool, shift: bool) -> Keys:
         if shift:
             return Keys.ShiftEscape
         return Keys.Escape
-    ctrl_key: Keys | None
+    _ctrl_key: Keys | None
     if base in _NAV_MAP:
-        shift_key, ctrl_key, ctrl_shift_key = _NAV_MAP[base]
+        shift_key, _ctrl_key, ctrl_shift_key = _NAV_MAP[base]
         if ctrl and shift:
             return ctrl_shift_key
         if ctrl:
-            return ctrl_key
+            return _ctrl_key
         if shift:
             return shift_key
         return base
@@ -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