DDD 3.3.12 (x86_64-pc-linux-gnu) gets `BadWindow' error

I was trying to get two array variables to display in different 
"Displays" windows. I hit the "Plot" button and got a message saying 
"Loading Gnuplot". Nothing happend, so after a while I hit Cancel and 
got this message in my terminal window:
---------------
[326] bryan: ddd testconvolve
X Error of failed request:  BadWindow (invalid Window parameter)
   Major opcode of failed request:  10 (X_UnmapWindow)
   Resource id in failed request:  0x0
   Serial number of failed request:  259087
   Current serial number in output stream:  259094
X Error of failed request:  BadWindow (invalid Window parameter)
   Major opcode of failed request:  10 (X_UnmapWindow)
   Resource id in failed request:  0x0
   Serial number of failed request:  259089
   Current serial number in output stream:  259424

X error (invalid Window parameter).

Oops!  You have found a bug in DDD.

If you can reproduce this bug, please send a bug report
to <[email protected]>, giving a subject like

     DDD 3.3.12 (x86_64-pc-linux-gnu) gets `BadWindow' error

To enable us to fix the bug, you should include the following information:
* What you were doing to get this message.  Report all the facts.
* The contents of the `~/.ddd/log' file as generated by this session.
Please read also the section "Reporting Bugs" in the DDD manual.

We thank you for your support.
---------------

A gzipped copy of ~/.ddd/log is attached.

Thanks,
-- 
Bryan
-
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