WAM crash when no input devices are found

I'm getting this error on a 8.0.0 image with WAM for the Raspberry Pi 3, just when booting up:

Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[int main(int, const char**)] ### Starting /usr/bin/WebAppMgr
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[virtual int WebRuntimeAGL::run(int, const char**)] WebRuntimeAGL::run
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[virtual int WebRuntimeAGL::run(int, const char**)] WebRuntimeAGL - creating SharedBrowserProcessRuntime
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[bool WamSocket::createSocket(bool)] service binding
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[void WebAppManagerServiceAGL::triggerStartupApp()] Triggering app start:
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: bool readJsonFromFile(const string&, Json::Value&): Failed to open file /etc/wam/com.webos.wam.json
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[int WamSocket::waitForMsg()] Waiting for data...
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[int main(int, const char**)] ### Starting /usr/bin/WebAppMgr
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[virtual int WebRuntimeAGL::run(int, const char**)] WebRuntimeAGL::run
Sep 26 16:06:51 raspberrypi3 WebAppMgr[471]: ## (DEBUG)[virtual int WebRuntimeAGL::run(int, const char**)] WebRuntimeAGL - creating RenderProcessRuntime
Sep 26 16:06:52 raspberrypi3 WebAppMgr[471]: [0926/160652.120358:ERROR:wayland_connection.cc(87)] No wl_seat object
Sep 26 16:06:52 raspberrypi3 WebAppMgr[471]: [0926/160652.129288:FATAL:ozone_platform_wayland.cc(148)] Failed to initialize Wayland platform
Sep 26 16:06:52 raspberrypi3 audit[471]: ANOM_ABEND auid=4294967295 uid=1001 gid=1001 ses=4294967295 subj=System pid=471 comm="WebAppMgr" exe="/usr/bin/WebAppMgr" sig=5 res=1
Sep 26 16:06:52 raspberrypi3 kernel: Unhandled prefetch abort: breakpoint debug exception (0x002) at 0x72955218
Sep 26 16:06:52 raspberrypi3 kernel: audit: type=1701 audit(1569514012.113:4): auid=4294967295 uid=1001 gid=1001 ses=4294967295 subj=System pid=471 comm="WebAppMgr" exe="/usr/bin/WebAppMgr" sig=5 res=1
Sep 26 16:06:52 raspberrypi3 systemd[1]: Created slice system-systemd\x2dcoredump.slice.
Sep 26 16:06:52 raspberrypi3 systemd[1]: Started Process Core Dump (PID 501/UID 0).
Sep 26 16:06:52 raspberrypi3 afbd-launcher@0.1[447]: Sleep 1 sec to resolve race condtion between HomeScreen and Launcher
Sep 26 16:06:52 raspberrypi3 systemd[1]: WebAppMgr@1001.service: Main process exited, code=dumped, status=5/TRAP
Sep 26 16:06:52 raspberrypi3 systemd[1]: WebAppMgr@1001.service: Failed with result 'core-dump'.

This seems unrelated to SPEC-2790; the cause of that bug doesn't apply here, and error messages are different.

It's strange that we didn't caught this problem earlier. We had tested 8.0.0 on the Pi before release; I think there is some randomness or race condition in this problem, it doesn't always crash. Other hardware is not affected.

[EDIT: it was caused by missing input devices on bootup. Might affect other platforms, pending to check this]