Qt/macOS: unpausing won't update display

[lunasorcery]

Pausing the emulation will correctly pause the display, unpausing will resume emulation but the display will be stuck on the paused frame. Further pauses will update the display to new paused frames but will never resume live visuals. This occurs with both Cmd+P and pausing via the menu.

Observed on a3d5e34 (latest master at time of posting).
Appears to have been introduced at ca85595 (checked via git bisect).
Only occurs on the Qt build - SDL version is unaffected.
This affects both GB and GBA emulation.
Observed on macOS 10.14.6, on a 2016 MBP (2.9 GHz Intel Core i5, Intel Iris Graphics 550 1536 MB)

[endrift]

I assume this also happens with the OpenGL 1.x display driver, but not with the Software display driver?

[lunasorcery]

Yes - this only seems to occur on the GL and GL 1.x drivers, Software appears unaffected.

I've got a change at lunasorcery@2d3c13c that appears to resolve it but I'm not confident it's the 'correct' fix.