Info panel: white text on white background on text files preview while using a dark theme makes previews useless

[angus]

Description: Ubuntu 20.04.3 LTS
Release: 20.04
dolphin:
  Installed: 4:19.12.3-0ubuntu1
  Candidate: 4:19.12.3-0ubuntu1

You know that dark themes display normal text as white on a dark background.
Dolphin information panel display text file previews always with white background: when normal text is white, it shows previews as WHITE on WHITE,as you can see on the screen shot.

STEPS TO REPRODUCE
1. Apply a dark theme in System-Settings->Appearance->Colors (i.e. Breeze Dark)
2. Open the Information Panel for a text file of size > 0

OBSERVED RESULT
A complete white page is shown instead of showing the content of the text file, you cannot read any text (see the screenshot).

EXPECTED RESULT
Text should be rendered with a different color than background OR a different background should be used other than white.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KUbuntu 20.04/Kde Plasma 5.18.5
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8

ADDITIONAL INFORMATION
1)
You can personalize text color by modifying "view text" property (System-settings->Appearance->Colors). It works as a workaround. However this change standard text color for all the KDE environment and not just the information panel view for text files!
2)
Text in bash scripts or text files with other extensions (.inc) display correctly even when using dark themes! Only .txt files show this problem.

UPSTREAM
Current release 19.12.3 is quite old and newer releases already patched this bug.

Could it be possible to merge upstream patch? Or upgrade to a more recent version of dolphin?