Use g_return_val_if_fail instead of g_return_if_fail, as the function now

Use g_return_val_if_fail instead of g_return_if_fail, as the function now

2000-09-01  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>

	* gstring.c (g_string_free): Use g_return_val_if_fail instead of
	g_return_if_fail, as the function now is supposed to return
	something.