Program received signal SIGSEGV, Segmentation fault.
0x000055555568d459 in need_war_player_hlp (actor=0x55555b891c10, act=18, target_tile=0x0, 
    target_city=0x55555ed7c570, target_unit=0x0) at ../../src/server/unithand.c:1024
1024      if (need_war_enabler(unit_type_get(actor), paction,
(gdb) bt
#0  0x000055555568d459 in need_war_player_hlp (actor=0x55555b891c10, act=18, 
    target_tile=0x0, target_city=0x55555ed7c570, target_unit=0x0)
    at ../../src/server/unithand.c:1024
#1  0x000055555568d561 in need_war_player (actor=0x55555b891c10, act_id=18, 
    target_tile=0x0, target_city=0x55555ed7c570, target_unit=0x0)
    at ../../src/server/unithand.c:1076
#2  0x000055555568e53f in expl_act_not_enabl (punit=0x55555b891c10, act_id=18, 
    target_tile=0x0, target_city=0x55555ed7c570, target_unit=0x0)
    at ../../src/server/unithand.c:1446
#3  0x0000555555690aef in illegal_action_msg (pplayer=0x5555568c55c0, 
    event=E_UNIT_ILLEGAL_ACTION, actor=0x55555b891c10, stopped_action=18, target_tile=0x0, 
    target_city=0x55555ed7c570, target_unit=0x0) at ../../src/server/unithand.c:2240
#4  0x00005555556925a6 in illegal_action (pplayer=0x5555568c55c0, actor=0x55555b891c10, 
    stopped_action_id=18, tgt_player=0x55555fbf2b60, target_tile=0x0, 
    target_city=0x55555ed7c570, target_unit=0x0, disturb_player=true, 
    requester=ACT_REQ_PLAYER) at ../../src/server/unithand.c:2849
#5  0x0000555555694b7d in unit_perform_action (pplayer=0x5555568c55c0, actor_id=9031, 
    target_id=5973, sub_tgt_id_incoming=0, name=0x555555941f2d "", action_type=18, 
    requester=ACT_REQ_PLAYER) at ../../src/server/unithand.c:3460
#6  0x0000555555692c47 in unit_do_action (pplayer=0x5555568c55c0, actor_id=9031, 
    target_id=5973, sub_tgt_id=0, name=0x555555941f2d "", action_type=18)
    at ../../src/server/unithand.c:3032
#7  0x000055555574a74a in dai_diplomat_city (ait=0x555555c086a0 <ai_types>, 
    punit=0x55555b891c10, ctarget=0x55555ed7c570)
    at ../../../src/ai/default/aidiplomat.c:393
#8  0x000055555574c6dd in dai_manage_diplomat (ait=0x555555c086a0 <ai_types>, 
    pplayer=0x5555568c55c0, punit=0x55555b891c10)
    at ../../../src/ai/default/aidiplomat.c:866
#9  0x000055555572075b in dai_manage_unit (ait=0x555555c086a0 <ai_types>, 
    pplayer=0x5555568c55c0, punit=0x55555b891c10) at ../../../src/ai/default/aiunit.c:2598
#10 0x000055555572152a in dai_manage_units (ait=0x555555c086a0 <ai_types>, 
    pplayer=0x5555568c55c0) at ../../../src/ai/default/aiunit.c:2789
#11 0x000055555570e2b1 in dai_do_first_activities (ait=0x555555c086a0 <ai_types>, 
    pplayer=0x5555568c55c0) at ../../../src/ai/default/aihand.c:744
#12 0x00005555556a063d in cai_do_first_activities (pplayer=0x5555568c55c0)
    at ../../../src/ai/classic/classicai.c:448
#13 0x000055555559ecd2 in ai_start_phase () at ../../src/server/srv_main.c:1064
#14 0x000055555559fe6c in begin_phase (is_new_phase=true)
    at ../../src/server/srv_main.c:1293
#15 0x00005555555a54ba in srv_running () at ../../src/server/srv_main.c:2770
#16 0x00005555555a73ab in srv_main () at ../../src/server/srv_main.c:3420
#17 0x00005555555976a7 in main (argc=6, argv=0x7fffffffe098)
    at ../../src/server/civserver.c:481