Example 20 failed with ValueError: cannot convert float NaN to integer #81

> python examples.py
Running: Example 20
Traceback (most recent call last):
  File "~/sourcecode/examples.py", line 240, in <module>
    for example in examples[20:]: example()
  File "~/sourcecode/examples.py", line 33, in wrapped
    fn()
  File "~/sourcecode/examples.py", line 230, in example20
    pbar.start()
  File "~/.local/lib/python3.10/site-packages/progressbar/progressbar.py", line 291, in start
    self.update(0)
  File "~/.local/lib/python3.10/site-packages/progressbar/progressbar.py", line 262, in update
    self.fd.write(self._format_line() + '\r')
  File "~/.local/lib/python3.10/site-packages/progressbar/progressbar.py", line 222, in _format_line
    widgets = ''.join(self._format_widgets())
  File "~/.local/lib/python3.10/site-packages/progressbar/progressbar.py", line 202, in _format_widgets
    widget = widgets.format_updatable(widget, self)
  File "~/.local/lib/python3.10/site-packages/progressbar/widgets.py", line 39, in format_updatable
    if hasattr(updatable, 'update'): return updatable.update(pbar)
  File "~/.local/lib/python3.10/site-packages/progressbar/widgets.py", line 230, in update
    return '%3d%%' % pbar.percentage()
ValueError: cannot convert float NaN to integer