[Freeciv-Dev] (PR#4758) client crash on goto

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

With the "return to nearest city" operation:

[1]+  Segmentation fault      (core dumped) ./civ

#0  pft_concat (dest_path=0x8672c00, src_path=0x0) at pf_tools.c:398
398         dest_path->length = src_path->length;
(gdb) bt
#0  pft_concat (dest_path=0x8672c00, src_path=0x0) at pf_tools.c:398
#1  0x0806dedc in send_goto_route (punit=0x8471a88) at goto.c:501
#2  0x0806b17c in request_unit_return (punit=0x1) at control.c:671
#3  0x401a5bb8 in gtk_item_factory_callback_marshal (widget=0x82b8fe0,
     func_data=0x8672bf8) at gtkitemfactory.c:263

(gdb) select 1

(gdb) p goto_map.num_parts
$2 = 1

(gdb) p goto_map.parts[0]
$3 = {start_moves_left = 0, start_x = 25, start_y = 30, end_moves_left = 
101,
   end_x = 25, end_y = 30, path = 0x0, map = 0x86807f0}

(gdb) p *goto_map.parts[0].map
$5 = {x = 25, y = 30, index = 617, params = 0x8659cf0, queue = 0x8681f70,
   lattice = 0x8692760, status = 0x8685a98 "", danger_queue = 0x0,
   d_lattice = 0x0}

(gdb) p *punit
$7 = {type = 4, id = 519, owner = 0, x = 25, y = 30, veteran = true,
   homecity = 338, moves_left = 0, hp = 7, unhappiness = 0, upkeep = 0,
   upkeep_food = 0, upkeep_gold = 0, foul = false, fuel = 0, bribe_cost 
= 0,
   ai = {control = false, ai_role = AIUNIT_NONE, ferryboat = 0, 
passenger = 0,
     bodyguard = 0, charge = 0}, activity = ACTIVITY_IDLE, goto_dest = 
{x = 27,
     y = 32}, activity_count = 0, activity_target = S_NO_SPECIAL,
   focus_status = FOCUS_AVAIL, ord_map = 0, ord_city = 0, moved = false,
   paradropped = false, connecting = false, transported_by = -1, pgr = 0x0

I've seen this before, but I don't know what causes it.  Why does the 
goto_map 'part' have the same starting and ending position?

jason