The FE mod has been slightly revised.

Therefore, the references that are held in the old mod options wont be valid anymore and you will receive an error as a result if you haven't removed your old config data for V1.0.

To correct this or remove the old mod options goto (default):

"C:/Users/{User}/AppData/LocalLow/Ludeon studios/RimWorld by Ludeon Studios/Config"

then find the file relating to FireExtinguisher. You need to delete this file.

You will also need to reset or now apply new mod options in game.

Further assistance regarding flushing of config data can be found on the RW discord in the troubleshooting channel.