Themed scrollbars, clicking into the scrollarea may draw unthemed unintentionally like in RosBE2.1.6 EULA

Reproduction steps

• activate Lunar theme
• run the RosBE 2.1.6 setup from rapps until its EULA
• click the scrollarea (not the triangle-buttons!) and hold the click to make the bar scroll

Expected result
It should continue to draw themed

Observed result
It breaks the theming for a moment 0.4.15-dev-3147-g3bf7e3a_affected_ClickNHoldMayBreakTheTheming.webm
although in some other dialogs like in Explorer-filebrowser this does not happen

Sidenote
No such problem in classic mode