[HuidaeCho]

This PR fixes the following error on a fresh startup in Windows:

(grass) C:\Users\hcho>grass --version
-C:\Users\hcho\AppData\Roaming\GRASS8--
Traceback (most recent call last):
  File "C:\Users\hcho\opt\micromamba\envs\grass\Library\bin\\..\lib\grass85\etc\grass_main.py", line 2535, in <module>
    main()
    ~~~~^^
  File "C:\Users\hcho\opt\micromamba\envs\grass\Library\bin\\..\lib\grass85\etc\grass_main.py", line 2205, in main
    grass_config_dir = create_grass_config_dir()
  File "C:\Users\hcho\opt\micromamba\envs\grass\Library\bin\\..\lib\grass85\etc\grass_main.py", line 397, in create_grass_config_dir
    old_mac_dir = os.path.join(os.getenv("HOME"), f".grass{GRASS_VERSION_MAJOR}")
  File "<frozen ntpath>", line 100, in join
TypeError: expected str, bytes or os.PathLike object, not NoneType

Windows does not have HOME and old_mac_dir should only be evaluated for MACOS.