cmake-gui: Theme breakage progressively since 3.19.0 on macOS

I've noticed progressively worsening UI problems with cmake-gui on macOS. CMake 3.18 seemed ok. From 3.19.0, the arrows for expanding variable groups seem to be white instead of dark, which makes the arrows either invisible or barely visible depending on which row they appear on. With 3.19.2, the background of the whole dialog changed from the usual light grey to a much darker tone. The change in 3.19.2 looks like it is trying to honour the system preference for a dark theme, but apart from the window background, the rest of the UI has the same color scheme as before. With a much darker background, that obviously doesn't work well. I've attached three screenshots which show the progressive degradation.