VNC server: headless: program start fails

[Alec Leamas]

When starting the flatpak opencpn program, program fails with console message

opencpn:2): Gdk-ERROR **: 18:54:58.144: The program 'opencpn' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadAccess (attempt to access private resource denied)'.
  (Details: serial 380 error_code 10 request_code 130 (MIT-SHM) minor_code 1)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the GDK_SYNCHRONIZE environment
   variable to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)

Steps to reproduce

-Install flatpak and flathub as of https://flatpak.org/setup/Debian
-Enable the VNC server in the Raspbian gui.
-Disconnect any physical monitor.
-Install OpenCPN:
   flatpak install --user \
      https://dl.flathub.org/repo/appstream/org.opencpn.OpenCPN.flatpakref
- Start program in VNC client
     flatpak run org.opencpn.OpenCPN
- Watch error message as of above

System state

Raspberry 4/4GB
Raspbian 64 bit, updated as of yesterday.
Linux raspberrypi 5.15.32-v8+ #1538 SMP PREEMPT Thu Mar 31 19:40:39 BST 2022 aarch64 GNU/Linux
realvnc-vnc-server 6.9.1.46706.

Other info

This seems to be about the RealVNC server bundled with Raspbian. Using TightVNC or tigervnc opencpn starts without problems.

This bug was initially reported upstream at https://github.com/OpenCPN/OpenCPN/issues/2628 -- more details are available in this bug.