NULL pointer dereference on implicit read of AR specific record index

P-Net before 1.0.3 dereferences a NULL AR pointer when handling an implicit read request without a valid target AR UUID for a record index that requires an AR (AR specific indices 0xE000-0xEFFF, and the expected identification data of a slot or subslot). A remote unauthenticated attacker can send such a request to crash the device (denial of service).