sage: region_plot(x+y>0, (x,-20,20), (y,20,-20))

IndexError                                
Traceback (most recent call last)
Input In [168], in <cell line: 1>()
----> 1 region_plot(x+y>Integer(0), (x,-Integer(20),Integer(20)), (y, Integer(20),-Integer(20)))

File ~/GitBox/sage/src/sage/misc/decorators.py:491, in options.__call__.<locals>.wrapper(*args, **kwds)
    489     options['__original_opts'] = kwds
    490 options.update(kwds)
--> 491 return func(*args, **options)

File ~/GitBox/sage/src/sage/plot/contour_plot.py:1727, in region_plot(f, xrange, yrange, plot_points, incol, outcol, bordercol, borderstyle, borderwidth, alpha, **options)
   1723 g._set_extra_kwds(Graphics._extract_kwds_for_show(options,
   1724                                                   ignore=['xmin', 'xmax']))
   1726 if neqs == 0:
-> 1727     g.add_primitive(ContourPlot(xy_data_array, xrange, yrange,
   1728                                 dict(contours=[-1e-20, 0, 1e-20],
   1729                                      cmap=cmap,
   1730                                      fill=True, **options)))
   1731 else:
   1732     mask = numpy.asarray([[elt > 0 for elt in rows]
   1733                           for rows in xy_data_array],
   1734                          dtype=bool)

File ~/GitBox/sage/src/sage/plot/contour_plot.py:82, in ContourPlot.__init__(self, xy_data_array, xrange, yrange, options)
     80 self.xy_data_array = xy_data_array
     81 self.xy_array_row = len(xy_data_array)
---> 82 self.xy_array_col = len(xy_data_array[0])
     83 GraphicPrimitive.__init__(self, options)

IndexError: index 0 is out of bounds for axis 0 with size 0