Minetest segfault at 9029a34cc6a3b19c1a431fe3ba069c30a13321f

Crash just after connecting:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffe72eb700 (LWP 357)]
0x00007ffff5345ab8 in main_arena () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007ffff5345ab8 in main_arena () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x0000000000659126 in mapblock_mesh_generate_special(MeshMakeData*, MeshCollector&) ()
#2  0x000000000079733d in MapBlockMesh::MapBlockMesh(MeshMakeData*, irr::core::vector3d<short>) ()
#3  0x0000000000604859 in MeshUpdateThread::Thread() ()
#4  0x0000000000566fbb in JThread::TheThread(void*) ()
#5  0x00007ffff63d0e9a in start_thread (arg=0x7fffe72eb700) at pthread_create.c:308
#6  0x00007ffff508131d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#7  0x0000000000000000 in ?? ()

Crash when opening a door a second or two after connecting:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffe72eb700 (LWP 381)]
0x0000000000659124 in mapblock_mesh_generate_special(MeshMakeData*, MeshCollector&) ()
(gdb) bt
#0  0x0000000000659124 in mapblock_mesh_generate_special(MeshMakeData*, MeshCollector&) ()
#1  0x000000000079733d in MapBlockMesh::MapBlockMesh(MeshMakeData*, irr::core::vector3d<short>) ()
#2  0x0000000000604859 in MeshUpdateThread::Thread() ()
#3  0x0000000000566fbb in JThread::TheThread(void*) ()
#4  0x00007ffff63d0e9a in start_thread (arg=0x7fffe72eb700) at pthread_create.c:308
#5  0x00007ffff508131d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#6  0x0000000000000000 in ?? ()