Describe the bug
Can't show the plot

To Reproduce
Steps to reproduce the behavior:
Run
python -m chart

Expected behavior
Show histogram plot

Screenshots

Environment:

• Operating System: Windows 10
• Python version: Python 3.9.6 (tags/v3.9.6:db3ff76, Jun 28 2021, 15:26:21)
• Software versions:
  • Toga: 0.3.0.dev32
  • toga-char: 0.1.0

Additional context
Add any other context about the problem here.