this might be related to #23898.

reproduce:

• play a game using markets
• save
• delete the markets
• load if it didn't crash. here it did on the 3rd try.

(gdb) bt
#0  0x000000000054827f in Map::pathfindBuilding (this=0x7fffb006dea0, building=0x7fd79d4b7b90, canSwim=true, x=68, y=19, dx=0x7fd79cd75558, dy=0x7fd79cd7555c, verbose=false) at src/Map.cpp:4369
#1  0x000000000066cda8 in Unit::handleMovement (this=0x7fd79cd75510) at src/Unit.cpp:1874
#2  0x0000000000670143 in Unit::endOfAction (this=0x7fd79cd75510) at src/Unit.cpp:2296
#3  0x0000000000670771 in Unit::syncStep (this=0x7fd79cd75510) at src/Unit.cpp:526
#4  0x0000000000657d7e in Team::syncStep (this=0x7fd79cdccd50) at src/Team.cpp:949
#5  0x00000000004c1566 in Game::syncStep (this=0x7fffb006ce08, localTeam=0) at src/Game.cpp:1208
#6  0x00000000004b2e29 in Engine::run (this=0x7fffb006cd90) at src/Engine.cpp:366
#7  0x0000000000514641 in Glob2::run (this=0x7fffb007252f, argc=1, argv=0x7fffb0072608) at src/Glob2.cpp:317
#8  0x0000000000514a13 in main (argc=1, argv=0x7fffb0072608) at src/Glob2.cpp:409
(gdb) bt full 3
#0  0x000000000054827f in Map::pathfindBuilding (this=0x7fffb006dea0, building=0x7fd79d4b7b90, canSwim=true, x=68, y=19, dx=0x7fd79cd75558, dy=0x7fd79cd7555c, verbose=false) at src/Map.cpp:4369
        bx = 51200
        by = 51200
        teamMask = 0
        gradient = (Uint8 *) 0x4c9d03b910 <Address 0x4c9d03b910 out of bounds>
        currentg = 0 '\0'
        _PRETTY_FUNCTION_ = "bool Map::pathfindBuilding(Building*, bool, int, int, int*, int*, bool)"
#1  0x000000000066cda8 in Unit::handleMovement (this=0x7fd79cd75510) at src/Unit.cpp:1874
        map = (class Map *) 0x7fffb006dea0
        canSwim = true
        _PRETTY_FUNCTION_ = "void Unit::handleMovement()"
        dxTab = {-4, -2, 2, 4, 4, 2, -2, -4}
        dyTab = {-2, -4, -4, -2, 2, 4, 4, 2}
#2  0x0000000000670143 in Unit::endOfAction (this=0x7fd79cd75510) at src/Unit.cpp:2296
No locals.