LordAro opened the ticket and wrote:

Using r25022

Steps to reproduce:

1. startai
2. open AI Debug window
3. close AI Debug window
4. stopai
5. open AI Debug window
6. Boom.

Only crashes if you've opened the debug window before you stopped the AI.
Game does not have to be running, can be paused throughout.

gdb stacktrace:

Program received signal SIGSEGV, Segmentation fault.
0x000000000065281b in AI::IsPaused (company=1) at /home/lordaro/coding/ottd/cleantrunk/src/ai/ai_core.cpp:139
139 bool paused = Company::Get(company)->ai_instance->IsPaused();
(gdb) bt
# 0 0x000000000065281b in AI::IsPaused (company=1) at /home/lordaro/coding/ottd/cleantrunk/src/ai/ai_core.cpp:139
# 1 0x000000000065a545 in AIDebugWindow::AIDebugWindow (this=0x1470670, desc=0x1124e60, number=0) at /home/lordaro/coding/ottd/cleantrunk/src/ai/ai_gui.cpp:1041
# 2 0x0000000000653e46 in ShowAIDebugWindow (show_company=INVALID_OWNER) at /home/lordaro/coding/ottd/cleantrunk/src/ai/ai_gui.cpp:1516
# 3 0x00000000009a27c8 in MenuClickHelp (index=3) at /home/lordaro/coding/ottd/cleantrunk/src/toolbar_gui.cpp:1039
# 4 0x00000000009a5f76 in MainToolbarWindow::OnDropdownSelect (this=0x1401e50, widget=26, index=3) at /home/lordaro/coding/ottd/cleantrunk/src/toolbar_gui.cpp:1586
# 5 0x0000000000a1d829 in DropdownWindow::OnMouseLoop (this=0x14d0d10) at /home/lordaro/coding/ottd/cleantrunk/src/widgets/dropdown.cpp:294
# 6 0x0000000000a21342 in DecreaseWindowCounters () at /home/lordaro/coding/ottd/cleantrunk/src/window.cpp:1640
# 7 0x0000000000a23ee7 in InputLoop () at /home/lordaro/coding/ottd/cleantrunk/src/window.cpp:2704
# 8 0x000000000084a394 in GameLoop () at /home/lordaro/coding/ottd/cleantrunk/src/openttd.cpp:1447
# 9 0x00000000009f947c in VideoDriver_SDL::MainLoop (this=0x1301b00) at /home/lordaro/coding/ottd/cleantrunk/src/video/sdl_v.cpp:763
# 10 0x00000000008486a6 in ttd_main (argc=1, argv=0x7fffffffe268) at /home/lordaro/coding/ottd/cleantrunk/src/openttd.cpp:847
# 11 0x000000000085f5ca in main (argc=1, argv=0x7fffffffe268) at /home/lordaro/coding/ottd/cleantrunk/src/os/unix/unix.cpp:275

Reported version: trunk
Operating system: All

This issue was imported from FlySpray: https://bugs.openttd.org/task/5490