#4505: Breaks transparent mode if you have a theme set

[elucidsoft]

Description

Steps to Reproduce

1. Set theme to dark
2. Set chart background to 'transparent'

Expected Behavior

The chart background will remain transparent but other elements of the chart will still use dark theme.

Actual Behavior

The chart background ignores the transparent setting and it's a dark grey color pulling from the theme.

Reverting back to 3.49.1 fixes the issue.

[Sebastian-Webster]

Hi @elucidsoft, I'm sorry about that. Does #4542 fix the problem?