Prevent triggering N2 handover when the UE has no active PDU session
by adding an early check in nr_rrc_trigger_n2_ho(), so we avoid building
an invalid HO Required. This aligns with 3GPP TS 38.413 (§9.2.3.1), where
HANDOVER REQUIRED carries a PDU Session Resource List with at least one
PDU Session Resource Item (range 1..maxnoofPDUSessions).
Guido Casati
389d7a0246