neg is not affecting MATE's panels

Hello,

A user reported for Debian 11 that the neg shortcut (super-m) is not affecting the panels of MATE. See the screenshots:

The ff@debian window does get inverted (including the title because I checked the box in the plugin configuration), but the top panel (Applications Emplacements Système) is not getting inverted.

Cc-ing @alexarnaud

Samuel

Edited Aug 22, 2021 by Samuel Thibault

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