wxGUI stand-alone monitor: use `unset` to discard gisenv variables

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@51574 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/mapdisp/main.py

@@ -134,9 +134,9 @@ if __name__ == "__main__":
     for key in env.keys():
         if key.find(env_name) == 0:
             RunCommand('g.gisenv',
-                       set = '%s=' % key)
+                       unset = '%s' % key)
         if key == 'MONITOR' and env[key] == monName:
             RunCommand('g.gisenv',
-                       set = '%s=' % key)
+                       unset = '%s' % key)
     
     sys.exit(0)