Fixes a crash that could happen where you close the window while the
main window is hiding, and then the app mistakenly thinks that "all
windows are closed" and initiates shutdown while the main window is
still active but hidden.
If the user hits the "stop stream" button it'll transition in to
"stopping stream..." and will continue to output until the stream
reaches the timing in which "stop" was pressed.
However, if there is significant congestion, stopping the stream can
take far longer than the user may like. So there needs to be an option
to forcibly stop the stream in that case; pushing the "stop" button a
second time should allow the user to tell the stream/recording to stop
right away instead of waiting for the precise stop timing.
This allows using the functions via Qt message queue. The reason for
this is so a frontend API can queue these functions to call safely from
another thread.
