Ella Core panics on malformed ULNASTransport Message without a Request Type

Summary

Ella Core panics when processing malformed UL NAS Transport NAS messages without a Request Type.

Impact

An attacker able to send crafted NAS messages to Ella Core can crash the process, causing service disruption for all connected subscribers. No authentication is required.

Fix

Add a guard when receiving an UL NAS Message without a Request Type given no SM Context.