When a change is made to some code, it's important to delete your save files before playing the game or it will be buggy/unplayable.
Here how to delete your save files : 

Locate this folder :
C:/Users/yourusername/AppData/Roaming/RenPy/Lubrificanus
(Appdata is a hidden folder so make sure you can see those in your folder proprieties)

...and the save files are there. Delete them so you can start the game anew.