[BUG]: display of Pol_FieldBox is wrong

[ebknudsen]

Describe the bug
The display section of Pol_FieldBox component does not correspond to the geometry of the field simulated.
Instead some kind of rhomboid prism is drawn

The box simulated is centered on the origin and aligned with the principal axis - the coordinates of the lines drawn are simply wrong.

Screenshots
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OS and McStas/McXtrace version (please complete the following information):

• OS: Linux
• McCode variant: McStas
• Version: 3.8.5

Add your code / dataset
/*******************************************************************************

• Instrument: fieldbox
  *******************************************************************************/
  DEFINE INSTRUMENT fieldbox(L=1)

TRACE

COMPONENT origin = Progress_bar()
AT (0, 0, 0) RELATIVE ABSOLUTE

COMPONENT pfbox = Pol_FieldBox(
xwidth = 0.1, yheight = 0.1, zdepth = L)
AT( 0,0,0) RELATIVE origin

FINALLY
%{
%}

END

Additional context
Add any other context about the problem here.