debug and plot -- odd behavior?

[fork]

When I run a script with debug_on_error(1) set, I get kicked into the
 debugger
whenver I call plot() in my script.  Like so:

debug> dbwhere
stopped in C:\Documents and
Settings\fork\Desktop\Octave3.4.3_gcc4.5.2_20111025\Octave3.4.3_gcc4.5.2
\share\octave\3.4.3\m\plot\newplot.m
at  line 57

This is using Nit's latest windows build, but it has happened on all the 
windows builds that I can remember.  I don't know if it happens
 on real operating systems...

I looked at line 57, and I don't see any error() calls.

Seems like a bug, and I will file eventually, but I wonder if it is windows
only, or if there is a good reason.  It happens with BOTH gnuplot and fltk.