fix: fixed theme change from dark mode to light mode not working

[Sebastian-Webster]

Fixed chart theme change from dark mode to light mode not working

Changing a chart from dark mode to light mode with the options object wasn't working (example at https://github.com/Sebastian-Webster/apex-reproducible-example)
This pull request fixes that issue so dark mode charts can be changed to light mode successfully

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes

[elucidsoft]

This should not have been merged in as it breaks transparent completely.

[Sebastian-Webster]

The transparent background issue has been fixed in #4542