Global application palette is not reset after calling QApplication::setStyle()

How to reproduce:

• Be on a system where the default style doesn't work well with palettes (macOS, mostly)
• Set a custom palette and the style to Fusion.
• Set the style back to the native one.

You are stuck with the custom palette. Trying to save the original palette from the style used on start leads to ugly brown dialog windows. There is no way to reset the palette back to system default.

This is in direct contradiction with the documentation:
http://doc.qt.io/qt-5/qapplication.html#setStyle

When switching application styles, the color palette is set back to the initial colors or the system defaults. This is necessary since certain styles have to adapt the color palette to be fully style-guide compliant