Fix crash when platform is WLAN Pi Pro

[joshschmelzle]

Type of change

• [X] Bug fix (non-breaking change that fixes something)
• [ ] New feature (non-breaking change adding functionality)
• [ ] Breaking change (fix or feature changing existing functionality)
• [ ] Code quality improvement (refactor, performance improvements)
• [ ] Documentation update (readme, changelog, man page, etc.)
• [ ] Other (please specify):

Breaking change

Does this Pull Request introduce a breaking change?

No

Proposed change

Please describe the purpose of this change, the problem it solves, and why the change is necessary. Include code snippets or links to related documentation when applicable

This PR fixes the following crash which occurred when running v1.4.5 on the WLAN Pi Pro.

Oct 15 12:10:40 wlanpi-087 fpms[639]: Traceback (most recent call last):
Oct 15 12:10:40 wlanpi-087 fpms[639]:   File "/usr/sbin/fpms", line 5, in <module>
Oct 15 12:10:40 wlanpi-087 fpms[639]:     from fpms.__main__ import main
Oct 15 12:10:40 wlanpi-087 fpms[639]:   File "/opt/wlanpi-fpms/lib/python3.9/site-packages/fpms/__main__.py", line 3, in <module>
Oct 15 12:10:40 wlanpi-087 fpms[639]:     sys.exit(fpms.main())
Oct 15 12:10:40 wlanpi-087 fpms[639]:   File "/opt/wlanpi-fpms/lib/python3.9/site-packages/fpms/fpms.py", line 279, in main
Oct 15 12:10:40 wlanpi-087 fpms[639]:     oled.init()
Oct 15 12:10:40 wlanpi-087 fpms[639]:   File "/opt/wlanpi-fpms/lib/python3.9/site-packages/fpms/modules/wlanpi_oled.py", line 22, in init
Oct 15 12:10:40 wlanpi-087 fpms[639]:     device.init()
Oct 15 12:10:40 wlanpi-087 fpms[639]:   File "/opt/wlanpi-fpms/lib/python3.9/site-packages/fpms/modules/screen/luma.py", line 191, in init
Oct 15 12:10:40 wlanpi-087 fpms[639]:     device.contrast(128)
Oct 15 12:10:40 wlanpi-087 fpms[639]: NameError: name 'device' is not defined

Testing

Please explain how you tested this change manually, and if applicable, what new tests you added.

• [ ] Did you add new automated tests? If yes, explain which edge cases are covered.
• [ ] Does this change affect any existing tests? If so, how did you adjust them?
• [ ] Please provide test run results or screenshots if applicable.

Checklist

• [X] I have read the contribution guidelines and policies
• [X] I have targeted this PR against the correct git branch
• [ ] I ran the test suite and verified it succeeded
• [ ] I linked an approved GitHub issue to this PR (next section)
• [X] I have updated the changelog (if applicable)
• [ ] I have added or updated the documentation (if applicable)

Related Issues/PRs

• This PR fixes/closes issue #
• This PR is related to issue #
• This PR depends on/blocks PR #