msc: f_mo_call_establish: improve AoIP IE check

Check if the AoIP Transport Layer IE is present before checking its
value. This gives a more meaningful error than Dynamic Testcase Error if
it is not present.

Change-Id: I52fc829b017848b6afe7e637f1911a0976f9c91d
---
M msc/BSC_ConnectionHandler.ttcn
1 file changed, 17 insertions(+), 0 deletions(-)

diff --git a/msc/BSC_ConnectionHandler.ttcn b/msc/BSC_ConnectionHandler.ttcn
index f141955..4351e06 100644
--- a/msc/BSC_ConnectionHandler.ttcn
+++ b/msc/BSC_ConnectionHandler.ttcn
@@ -1605,6 +1605,10 @@
 		var BSSMAP_IE_SpeechCodec codec;
 		var BSSMAP_IE_Osmo_OsmuxCID osmuxCID;
 
+		if (not ispresent(bssap.pdu.bssmap.assignmentRequest.aoIPTransportLayer)) {
+			setverdict(fail, "MSC sent Assignment Request without AoIP Transport Layer IE");
+			mtc.stop;
+		}
 		if (not match(bssap.pdu.bssmap.assignmentRequest.aoIPTransportLayer, tla_ass1)
 		    and not match(bssap.pdu.bssmap.assignmentRequest.aoIPTransportLayer, tla_ass2)) {
 			log("Expected one of: 1:", tla_ass1, " 2:", tla_ass2);

