godot_openvr: Launching Godot (with ARVR support) Causes Eventual `godot_arvr_process` Seg Fault

I’m running Godot w/ARVR support on Ubuntu (19.04) + HTC Vive (generation 1). The crash pattern is:

1. Launch Godot w/o controller(s)

2. Turn on controller, generating the following console output (but Godot will keep running):

   Found openvr device 1 (vr_controller_vive_1_5)
   Creating render model resource
   OpenVR: increased use count to 2
   Argument count: 1
   Searching for: vr_controller_vive_1_5
   

3. Click controller, causing the following crash:

   handle_crash: Program crashed with signal 11
   Dumping the backtrace. Please include this when reporting the bug on https://github.com/godotengine/godot/issues
   [1] /lib/x86_64-linux-gnu/libc.so.6(+0x43f60) [0x7f89de6b1f60] (??:0)
   [2] /home/george/Simula/addons/godot-openvr/bin/x11/libgodot_openvr.so(+0x2b98) [0x7f89d4abfb98] (??:0)
   [3] ARVRInterfaceGDNative::process() (/home/george/SimulaMax/build/godot/modules/gdnative/arvr/arvr_interface_gdnative.cpp:212)
   [4] ARVRServer::_process() (/home/george/SimulaMax/build/godot/servers/arvr_server.cpp:352 (discriminator 2))
   [5] VisualServerViewport::draw_viewports() (/home/george/SimulaMax/build/godot/servers/visual/visual_server_viewport.cpp:252)
   [6] VisualServerRaster::draw(bool, double) (/home/george/SimulaMax/build/godot/servers/visual/visual_server_raster.cpp:107 (discriminator 2))
   [7] VisualServerWrapMT::draw(bool, double) (/home/george/SimulaMax/build/godot/servers/visual/visual_server_wrap_mt.cpp:104)
   [8] Main::iteration() (/home/george/SimulaMax/build/godot/main/main.cpp:1878)
   [9] OS_X11::run() (/home/george/SimulaMax/build/godot/platform/x11/os_x11.cpp:2959)
   [10] /home/george/Simula/addons/godot-haskell-plugin/../..//bin/godot(main+0xdc) [0x115b82e] (/home/george/SimulaMax/build/godot/platform/x11/godot_x11.cpp:56)
   [11] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xeb) [0x7f89de694b6b] (??:0)
   [12] /home/george/Simula/addons/godot-haskell-plugin/../..//bin/godot(_start+0x2a) [0x115b69a] (??:?)
   -- END OF BACKTRACE --
   

4. The fuller gdb backtrace output is as follows:

   Found openvr device 1 (vr_controller_vive_1_5)
   Creating render model resource
   OpenVR: increased use count to 2
   Argument count: 1
   Searching for: vr_controller_vive_1_5
   [New Thread 0x7fffbe195700 (LWP 5188)]
   
   Thread 1 "godot" received signal SIGSEGV, Segmentation fault.
   0x00007fffed32cb98 in godot_arvr_process (p_data=0x61074c0) at src/ARVRInterface.cpp:347
   347    src/ARVRInterface.cpp: No such file or directory.
   (gdb) bt
   #0  0x00007fffed32cb98 in godot_arvr_process(void*) (p_data=0x61074c0)
       at src/ARVRInterface.cpp:347
   #1  0x000000000154e494 in ARVRInterfaceGDNative::process() (this=0x6112190)
       at modules/gdnative/arvr/arvr_interface_gdnative.cpp:211
   #2  0x0000000002df1ac1 in ARVRServer::_process() (this=0x5af5cd0)
       at servers/arvr_server.cpp:356
   #3  0x0000000002fea1a0 in VisualServerViewport::draw_viewports() (this=0x4f207b0)
       at servers/visual/visual_server_viewport.cpp:250
   #4  0x0000000002fbc351 in VisualServerRaster::draw(bool, double)
       (this=0x4f1db60, p_swap_buffers=true, frame_step=0.019463000819087029)
       at servers/visual/visual_server_raster.cpp:106
   #5  0x0000000002ff0bee in VisualServerWrapMT::draw(bool, double)
   
       at servers/visual/visual_server_wrap_mt.cpp:102
   #6  0x000000000119713c in Main::iteration() () at main/main.cpp:1877
   #7  0x000000000116a5c9 in OS_X11::run() (this=0x7fffffffdb20)
       at platform/x11/os_x11.cpp:2959
   #8  0x000000000115b82e in main(int, char**) (argc=3, argv=0x7fffffffe298)
       at platform/x11/godot_x11.cpp:55
   

Someone else on a project I’m working on (@KaneTW) inspected libgodot_openvr with debug symbols and found that

arvr_api->godot_arvr_set_controller_button(arvr_data->trackers[event.trackedDeviceIndex], button, true);

is what is crashing, so that this could be a bug with libgodot_openvr.

Does anyone have any thoughts about how to fix this crash?