The monitor handle could have become invalid just before the call to
GetDpiForMonitor. It was possible for both window and monitor content
scale queries.
This ensures both that an appropriate error is emitted and that the
retrieved values are zero on error.
Fixes#1615
(cherry picked from commit fbfd7e65c842c7909b11747f0641364593304f1a)
Joysticks already connected when GLFW was initalized did not get gamepad
mappings applied to them.
Regression introduced by 74a8ba26c3b9bb830462ffbebefa133c38368fa3.
This change was backported without taking into account that 3.3.x does
not have on-demand joystick init.
Fixes#1996
