fix realloc-of-non-malloced pointer, and reduce size while at it

shell/hush.c

@@ -423,7 +423,7 @@ static const struct built_in_command bltins[] = {
 static const char *set_cwd(void)
 {
 	if (cwd == bb_msg_unknown)
-		cwd = NULL;     /* xrealloc_getcwd_or_warn(arg) called free(arg) */
+		cwd = NULL;     /* xrealloc_getcwd_or_warn(arg) calls free(arg)! */
 	cwd = xrealloc_getcwd_or_warn((char *)cwd);
 	if (!cwd)
 		cwd = bb_msg_unknown;