don't launch GUI dialogs from command line when GUI is text (fix when GUI is not defined)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@68148 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/gis/parser.c

@@ -437,7 +437,7 @@ int G_parser(int argc, char **argv)
     gui_envvar = G_getenv_nofatal("GUI");
     if (argc < 2 && (st->has_required || G__has_required_rule())
         && !st->no_interactive && isatty(0) &&
-        G_strcasecmp(gui_envvar, "text") != 0) {
+        (gui_envvar && G_strcasecmp(gui_envvar, "text") != 0)) {
 	if (module_gui_wx() == 0)
             return -1;
     }