Qt: Hangs on clicking break button soon after opening CLI debugger

[AntyMew]

Build: 0.6-4446-69a30f95
OS: Debian 9.0 stretch amd64

If the CLI debugger is opened and the "Break" button is hit, both while BIOS is booting, the emulator hangs.

[AntyMew]

On further testing, this appears to be time-sensitive from opening the CLI debugger to clicking "Break," rather than the more strict requirement of both during BIOS.