Ella Core panics on malformed ULNASTransport Message without a Request Type

Ella Core is a 5G core designed for private networks. Versions prior to 1.6.0 panic when processing malformed UL NAS Transport NAS messages without a Request Type. 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. Version 1.6.0 adds a guard when receiving an UL NAS Message without a Request Type given no SM Context.