840 - Incorrect background color for text thumbnails in inactive panel

[Dreamer]

To reproduce:
- use any dark color scheme, e.g. Dark grey flat default
- use thumbnails view in both panels
- in settings - thumbnails - add "txt" to field "Make thumbnails for the text files"
= thumbnails background color for text file(s) in inactive panel has color from active panel, it's not transparent

FC 840 64-bit donor, Windows 10 20H2 64-bit.

[Odamn-Ete]

confirmed

FreeCommander XE 2020 Build 840 64-bit donor
Windows 10 Pro 64-bit Version 20H2 Build 19042.685