xfwm4 4.14.5 crashes with 'BadPixmap (invalid Pixmap parameter)'

~/.xsession-errors message given below at the end of this ticket.
System is Arch Linux, up-to-date.
Only occurs with 4.14.5-1, downgrading to 4.14.4-1 or 4.14.3-1 resolves the issue.
This error is reproducible with MATLAB R2018a. I am uncertain how to trigger this in any other way.
Steps to reproduce:

In MATLAB, open a figure window, (you can do this by just typing 'figure' at the command line)
Use the command 'close all' to close the figure window you just created.
xfwm4 will crash and restart.
The error may not occur the first time, but after repeating this a few times, I have managed to reliably reproduced this error.
Eventually xfwm4 will fail to restart after crashing, leaving windows without a title bar and are effectively inoperable.

-------- Error log fron ~/.xsession-errors ---------

(xfwm4:14601): Gdk-ERROR **: 14:13:53.676: The program 'xfwm4' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadPixmap (invalid Pixmap parameter)'.
  (Details: serial 28428 error_code 4 request_code 54 (core protocol) minor_code 0)
  (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.)