iuup: Fix IPTIs_present not set to 0 if no IPTIs received

Related: SYS#5969
Change-Id: I503dc509ad8619f13cd83ae03261a2297e2b9fc7
diff --git a/src/gsm/iuup.c b/src/gsm/iuup.c
index edcea3b..2c70307 100644
--- a/src/gsm/iuup.c
+++ b/src/gsm/iuup.c
@@ -593,6 +593,7 @@
 		buf++;
 		itail = (struct iuup_ctrl_init_tail *)buf;
 	} else {
+		iui->config.IPTIs_present = false;
 		itail = (struct iuup_ctrl_init_tail *)ihdr_rfci;
 	}
 	if (itail->data_pdu_type > 1) {