I want to install `r.clip` Grass extension with Rstudio and `g.extension` but I have error `ERREUR : Variable 'LOCATION_NAME' non définie`. My code is :

    install.packages("rgrass7")
    library(rgrass7)
    
    # Creation Grass environment 
    initGRASS("C:/Program Files/GRASS GIS 7.6",
              override = TRUE,
              gisDbase = "GRASS_TEMP",
              home = tempdir(),
              mapset = "PERMANENT",
              remove_GISRC = TRUE)
    
    # To install extension 
    execGRASS(cmd = "g.extension",
              flags = "s",
              parameters = list(extension = "r.clip", operation = "add"))
    

And the code to install extension return this error : 

    > execGRASS(cmd = "g.extension",
    +           flags = "s",
    +           parameters = list(extension = "r.clip", operation = "add"))

    ATTENTION: Extension <r.clip> already installed. Re-installing...
    Downloading precompiled GRASS Addons <r.clip>...
    ERREUR :Variable 'LOCATION_NAME' non définie
    ERREUR :Variable 'LOCATION_NAME' non définie
    ERREUR :Variable 'LOCATION_NAME' non définie
    Traceback (most recent call last):
      File "C:/Program Files/GRASS GIS 7.6/scripts/g.extension.py", line 1748, in <module>
        sys.exit(main())
      File "C:/Program Files/GRASS GIS 7.6/scripts/g.extension.py", line 1727, in main
        install_extension(source=source, url=url, xmlurl=xmlurl)
      File "C:/Program Files/GRASS GIS 7.6/scripts/g.extension.py", line 702, in install_extension
        blist = install_extension_xml(xmlurl, mlist)
      File "C:/Program Files/GRASS GIS 7.6/scripts/g.extension.py", line 922, in install_extension_xml
        write_xml_modules(xml_file, tree)
      File "C:/Program Files/GRASS GIS 7.6/scripts/g.extension.py", line 601, in write_xml_modules
        libgis_revison = grass.version()['libgis_revision']
    KeyError: 'libgis_revision'

    > execGRASS(cmd = "r.clip",
    +           flags = "overwrite",
    +           parameters = list (input = "GRASS_MNS",
    +                              output = "GRASS_MNT_crop"))

    Error : XML content does not seem to be XML: ' No such file or directory'
    De plus : Warning message:
    In system(cmd0, intern = TRUE) :
      l'exécution de la commande 'r.clip.bat --interface-description' renvoie un statut 2
    Error in parseGRASS(cmd, legacyExec = legacyExec) : r.clip not parsed


When I check the manuel of the `g.extension` function, I saw that `-s` argument in `flags` can to be use but the system administrator rights are necessary. So I have given the right at my folder where Grass 7.6 is installed and I'm administrator of my computer.

When I install `r.clip` in Grass interface, installation is successfully finished but it's impossible to find `r.clip` extension in extension list of Grass.

[![enter image description here][1]][1]

[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/XlqiJ.png
  [2]: https://i.sstatic.net/5vL9s.png
 
But when I research `r.clip` extension in Rstudio with code below, I find it !

    > execGRASS(cmd = "g.extension",
    +           flags = "l")

    ATTENTION: GRASS_ADDON_BASE is not defined, installing to ~/.grass7/addons
    List of available extensions (modules):
    r.clip
    ...

I use Grass 7.6.1 installed in `C:/Program Files/GRASS GIS 7.6` and R 3.6.1.

Thanks you in advence for your help !