After the game become sandbox,i can't save the game and instantly give me error the moment i try to save as the end the prolog and start to be sandbox
```
I'm sorry, but an uncaught exception occurred.
While running game code:
File "renpy/common/00action_file.rpy", line 382, in __call__
File "game/scripts/01checkpoints.rpy", line 74, in save_checkpoint_file
KeyError: u'file_name'
-- Full Traceback ------------------------------------------------------------
Full traceback:
File "_layout/screen_load_save.rpymc", line 35, in script
File "renpy/ast.py", line 928, in execute
File "renpy/python.py", line 2247, in py_exec_bytecode
File "renpy/common/_layout/screen_load_save.rpym", line 35, in <module>
File "renpy/ui.py", line 298, in interact
File "renpy/display/core.py", line 3371, in interact
File "renpy/display/core.py", line 4206, in interact_core
File "renpy/display/layout.py", line 1101, in event
File "renpy/display/transition.py", line 48, in event
File "renpy/display/layout.py", line 1101, in event
File "renpy/display/layout.py", line 1101, in event
File "renpy/display/screen.py", line 727, in event
File "renpy/display/layout.py", line 1101, in event
File "renpy/display/layout.py", line 1323, in event
File "renpy/display/layout.py", line 273, in event
File "renpy/display/layout.py", line 1101, in event
File "renpy/display/layout.py", line 1101, in event
File "renpy/display/behavior.py", line 982, in event
File "renpy/display/behavior.py", line 917, in handle_click
File "renpy/display/behavior.py", line 323, in run
File "renpy/display/behavior.py", line 330, in run
File "renpy/common/00action_file.rpy", line 382, in __call__
File "renpy/loadsave.py", line 430, in save
File "game/scripts/01checkpoints.rpy", line 74, in save_checkpoint_file
KeyError: u'file_name'
```