tools: Fix handling of empty argv in various minor GLib tools

This won’t really affect anything, but we might as well fix them to not
crash if called with an empty `argv` by someone (ab)using `execve()`.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

gio/gdbus-tool.c

@@ -107,7 +107,7 @@ usage (gint *argc, gchar **argv[], gboolean use_stdout)
   g_option_context_set_help_enabled (o, FALSE);
   /* Ignore parsing result */
   g_option_context_parse (o, argc, argv, NULL);
-  program_name = g_path_get_basename ((*argv)[0]);
+  program_name = (*argc > 0) ? g_path_get_basename ((*argv)[0]) : g_strdup ("gdbus-tool");
   s = g_strdup_printf (_("Commands:\n"
                          "  help         Shows this information\n"
                          "  introspect   Introspect a remote object\n"
@@ -141,6 +141,7 @@ modify_argv0_for_command (gint *argc, gchar **argv[], const gchar *command)
    *  2. save old argv[0] and restore later
    */
 
+  g_assert (*argc > 1);
   g_assert (g_strcmp0 ((*argv)[1], command) == 0);
   remove_arg (1, argc, argv);
 

gio/gio-querymodules.c

@@ -161,7 +161,7 @@ main (gint   argc,
 {
   int i;
 
-  if (argc == 1)
+  if (argc <= 1)
     {
       g_print ("Usage: gio-querymodules <directory1> [<directory2> ...]\n");
       g_print ("Will update giomodule.cache in the listed directories\n");