I'm sorry, but an uncaught exception occurred.
While running game code:
  File "game/ascript/mlf_house.rpy", line 75, in script
    call screen but_nav('mlf_house.hall')
  File "renpy/common/000statements.rpy", line 531, in execute_call_screen
    store._return = renpy.call_screen(name, *args, **kwargs)
  File "game/ascript/inventory.rpy", line 133, in execute
    screen inventory_useitem(item) tag inv:
  File "game/ascript/inventory.rpy", line 133, in execute
    screen inventory_useitem(item) tag inv:
  File "game/ascript/inventory.rpy", line 137, in execute
    if item == i_laptop and not laptop_lock:
NameError: name 'laptop_lock' is not defined