gsup_client_mux_tx_error_reply(): fix: do not omit session IEs

For SS/USSD, it's important to have both session state and ID IEs.
Found using the new TC_mt_ussd_for_unknown_subscr test case.

Change-Id: I57317a7b8036d1ffd36e2021efc146db4633da84
Related: (TTCN-3) Id35cd3ec15d1bab15260312d7bbb41e2d10349fe
Related: OS#2931
1 file changed