widelands: ../src/graphic/gl/road_program.cc:75: void RoadProgram::add_road(int, int, const FieldsToDraw::Field&, const FieldsToDraw::Field&, float, Widelands::RoadType, RoadProgram::Direction, uint32_t*): Assertion `start.owner != nullptr' failed.

Thread 1 "widelands" received signal SIGABRT, Aborted.
__GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:58
58	../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:58
#1  0x00007ffff515f40a in __GI_abort () at abort.c:89
#2  0x00007ffff5156e47 in __assert_fail_base (fmt=<optimized out>, assertion=assertion@entry=0x142ac92 "start.owner != nullptr", 
    file=file@entry=0x142ac70 "../src/graphic/gl/road_program.cc", line=line@entry=75, 
    function=function@entry=0x142ae00 <RoadProgram::add_road(int, int, FieldsToDraw::Field const&, FieldsToDraw::Field const&, float, Widelands::RoadType, RoadProgram::Direction, unsigned int*)::__PRETTY_FUNCTION__> "void RoadProgram::add_road(int, int, const FieldsToDraw::Field&, const FieldsToDraw::Field&, float, Widelands::RoadType, RoadProgram::Direction, uint32_t*)")
    at assert.c:92
#3  0x00007ffff5156ef2 in __GI___assert_fail (assertion=0x142ac92 "start.owner != nullptr", file=0x142ac70 "../src/graphic/gl/road_program.cc", line=75, 
    function=0x142ae00 <RoadProgram::add_road(int, int, FieldsToDraw::Field const&, FieldsToDraw::Field const&, float, Widelands::RoadType, RoadProgram::Direction, unsigned int*)::__PRETTY_FUNCTION__> "void RoadProgram::add_road(int, int, const FieldsToDraw::Field&, const FieldsToDraw::Field&, float, Widelands::RoadType, RoadProgram::Direction, uint32_t*)") at assert.c:101
#4  0x000000000116a9ef in RoadProgram::add_road (this=0x30f61e0, renderbuffer_width=1152, renderbuffer_height=864, start=..., end=..., scale=1, road_type=Widelands::kNormal, 
    direction=RoadProgram::kEast, gl_texture=0x7fffffff8fcc) at ../src/graphic/gl/road_program.cc:75
#5  0x000000000116b001 in RoadProgram::draw (this=0x30f61e0, renderbuffer_width=1152, renderbuffer_height=864, fields_to_draw=..., scale=1, z_value=0.999847412)
    at ../src/graphic/gl/road_program.cc:147
#6  0x000000000105dde4 in RenderQueue::draw_items (this=0x18f2960 <RenderQueue::instance()::render_queue>, items=std::vector of length 396, capacity 512 = {...})
    at ../src/graphic/render_queue.cc:255
#7  0x000000000105da63 in RenderQueue::draw (this=0x18f2960 <RenderQueue::instance()::render_queue>, screen_width=1152, screen_height=864) at ../src/graphic/render_queue.cc:209
#8  0x0000000000ccbb5c in Graphic::refresh (this=0x19542b0) at ../src/graphic/graphic.cc:213
#9  0x0000000000ebf5e9 in UI::Panel::do_run (this=0x2f81b90) at ../src/ui_basic/panel.cc:197
#10 0x0000000000c1f33a in UI::Panel::run<UI::Panel::Returncodes> (this=0x2f81b90) at ../src/ui_basic/panel.h:96
#11 0x0000000000d2d023 in Widelands::Game::run (this=0x7fffffffb2d0, loader_ui=0x7fffffff9710, start_game_type=Widelands::Game::Loaded, script_to_run="", replay=false, 
    prefix_for_replays="single_player") at ../src/logic/game.cc:525
#12 0x0000000000d2c48e in Widelands::Game::run_load_game (this=0x7fffffffb2d0, filename="save/crash_road2.wgf", script_to_run="") at ../src/logic/game.cc:383
#13 0x0000000000c19e4c in WLApplication::load_game (this=0x191e980) at ../src/wlapplication.cc:1263
#14 0x0000000000c18fa0 in WLApplication::mainmenu_singleplayer (this=0x191e980) at ../src/wlapplication.cc:1097
#15 0x0000000000c1898a in WLApplication::mainmenu (this=0x191e980) at ../src/wlapplication.cc:999
#16 0x0000000000c154be in WLApplication::run (this=0x191e980) at ../src/wlapplication.cc:442
#17 0x0000000000c13b51 in main (argc=1, argv=0x7fffffffd9e8) at ../src/main.cc:49