Core segfaults when trying to use the software renderer with Vulkan video driver

Hi there,

I've just build an amd64 version on Debian with latest stable MESA, using latest RetroArch sources from github to run it, and I found it segfaults if I run it with the software renderer:

Thread 1 "retroarch" received signal SIGSEGV, Segmentation fault.
0x00007ffff3665f2c in GSDevice::ClearCurrent (this=0x0) at /root/src/libretro/ps2/pcsx2/GS/Renderers/Common/GSDevice.cpp:346
346             m_current = nullptr;
(gdb) bt
#0  0x00007ffff3665f2c in GSDevice::ClearCurrent (this=0x0) at /root/src/libretro/ps2/pcsx2/GS/Renderers/Common/GSDevice.cpp:346
#1  0x00007ffff3667567 in GSRenderer::Reset (this=0x5555560dd2e0, hardware_reset=true)
    at /root/src/libretro/ps2/pcsx2/GS/Renderers/Common/GSRenderer.cpp:38
#2  0x00007ffff347a3d5 in MTGS::MainLoop (flush_all=false) at /root/src/libretro/ps2/pcsx2/MTGS.cpp:248
#3  0x00007ffff3464264 in retro_run () at /root/src/libretro/ps2/libretro/main.cpp:1731
#4  0x00005555555dc8c1 in core_run ()
#5  0x00005555555df5fd in runloop_iterate ()
#6  0x00005555555d5bc5 in rarch_main ()
#7  0x00007ffff773ad68 in __libc_start_call_main (main=main@entry=0x5555555c7200 <main>, argc=argc@entry=4, 
    argv=argv@entry=0x7fffffffe288) at ../sysdeps/nptl/libc_start_call_main.h:58
#8  0x00007ffff773ae25 in __libc_start_main_impl (main=0x5555555c7200 <main>, argc=4, argv=0x7fffffffe288, init=<optimized out>, 
    fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffe278) at ../csu/libc-start.c:360
#9  0x00005555555c72b1 in _start ()

OTOH, Vulkan and ParallelGS renderers both work fine, only the software renderer seems to be affected.

This is how I configure the souces to build:

cmake .. -DUSE_OPENGL=FALSE

Any ideas on what could be going on? It seems that, in general, software renderer should be working.
Maybe it doesn't work with the RetroArch Vulkan backend for some reason?

Start with GSDevice::ClearCurrent in GS/Renderers/Common/GSDevice.cpp:346 and GSRenderer::Reset in GS/Renderers/Common/GSRenderer.cpp:38, using the supplied backtrace and software-renderer build configuration. Reproduce with the RetroArch Vulkan backend, then trace the initialization path through MTGS::MainLoop and libretro/main.cpp. Done means the software renderer no longer segfaults while Vulkan and ParallelGS behavior remains intact.