Show Video Thumbnails settings : doesn't work on group with "group by folder" option.

When you disable the Video Thumbnails settings (Settings > Interface > Video), thumbnails are still here for group with "group by folder" option.

Side question : shouldn't we delete the previously generated thumbnails if this setting is disabled ? Some users disable it to save space in their device and it's not the case. Also it could be useful for developers to quickly test thumbnail generation issues, without clear all the medialibrary

Screenshot / video

Context

App version

3.5.3-beta-1 (Play Store)

Android version

Device model

Xperia 10 III