begin_contour and end_contour not working

[ziyaointl]

Describe the bug
An error was thrown when using begin_contour and end_contour. If I delete the block of code that describes the contour (i.e. leaving the code that uses begin_shape and end_shape) the program runs as expected.

To Reproduce

from p5 import *

def draw():
	translate(50, 50)
	stroke(255, 0, 0)
	begin_shape()
	# Exterior part of shape, clockwise winding
	vertex(-40, -40)
	vertex(40, -40)
	vertex(40, 40)
	vertex(-40, 40)
	# # Interior part of shape, counter-clockwise winding
	begin_contour()
	vertex(-20, -20)
	vertex(-20, 20)
	vertex(20, 20)
	vertex(20, -20)
	end_contour()
	end_shape('CLOSE')

run(mode="P2D")

Expected behavior
A square ring is displayed on the screen.
Example from https://p5js.org/reference/#/p5/beginContour

System information:

• p5 release (version number or latest commit): commit fb9373c
• Python version: Python 3.7.7
• Operating system: Ubuntu 18.04 LTS

Additional context
Stderr:

WARNING: Traceback (most recent call last):
  File "/home/ziyao/Github/p5/test.py", line 34, in <module>
    run(mode="P2D")
  File "/home/ziyao/Github/p5/p5/sketch/userspace.py", line 161, in run
    app.run()
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/app/_default_app.py", line 62, in run
    return default_app.run()
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/app/application.py", line 152, in run
    return self._backend._vispy_run()
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/app/backends/_glfw.py", line 194, in _vispy_run
    self._vispy_process_events()
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/app/backends/_glfw.py", line 183, in _vispy_process_events
    timer._tick()
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/app/backends/_glfw.py", line 516, in _tick
    self._vispy_timer._timeout()
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/app/timer.py", line 168, in _timeout
    count=self.iter_count)
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/util/event.py", line 455, in __call__
    self._invoke_callback(cb, event)
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/util/event.py", line 475, in _invoke_callback
    self, cb_event=(cb, event))
  << caught exception here: >>
  File "/home/ziyao/.local/lib/python3.7/site-packages/vispy/util/event.py", line 471, in _invoke_callback
    cb(event)
  File "/home/ziyao/Github/p5/p5/sketch/base.py", line 105, in on_timer
    self.draw_method()
  File "/home/ziyao/Github/p5/test.py", line 32, in draw
    end_shape('CLOSE')
  File "/home/ziyao/Github/p5/p5/core/primitives.py", line 70, in wrapped
    draw_shape(s)
  File "/home/ziyao/Github/p5/p5/core/primitives.py", line 588, in draw_shape
    draw_shape(child_shape)
  File "/home/ziyao/Github/p5/p5/core/primitives.py", line 582, in draw_shape
    p5.renderer.render(shape)
  File "/home/ziyao/Github/p5/p5/sketch/renderer2d.py", line 219, in render
    vertices = shape._draw_vertices
  File "/home/ziyao/Github/p5/p5/core/shape.py", line 363, in _draw_vertices
    self._retriangulate()
  File "/home/ziyao/Github/p5/p5/core/shape.py", line 333, in _retriangulate
    segments=triangulation_segments, holes=self.get_interior_point(self.contour))
  File "/home/ziyao/Github/p5/p5/core/shape.py", line 313, in get_interior_point
    if vertex not in shape_vertices:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
ERROR: Invoking <bound method Sketch.on_timer of <Sketch (Glfw) at 0x7efe85c96d10>> for Event
ERROR: Invoking <bound method Sketch.on_timer of <Sketch (Glfw) at 0x7efe85c96d10>> repeat 2
ERROR: Invoking <bound method Sketch.on_timer of <Sketch (Glfw) at 0x7efe85c96d10>> repeat 4
ERROR: Invoking <bound method Sketch.on_timer of <Sketch (Glfw) at 0x7efe85c96d10>> repeat 8
ERROR: Invoking <bound method Sketch.on_timer of <Sketch (Glfw) at 0x7efe85c96d10>> repeat 16
ERROR: Invoking <bound method Sketch.on_timer of <Sketch (Glfw) at 0x7efe85c96d10>> repeat 32
ERROR: Invoking <bound method Sketch.on_timer of <Sketch (Glfw) at 0x7efe85c96d10>> repeat 64
ERROR: Invoking <bound method Sketch.on_timer of <Sketch (Glfw) at 0x7efe85c96d10>> repeat 128