When the message loop is active and we get an incoming dispatch() event,
we'll just handle it directly. In practice this would only be needed
when the event is a response to an `audioMaster()` call made during the
event loop, but we can't know that. This allows the `getProgram()`
during `audioMasterUpdateDisplay()` in REAPER and Renoise to work
correctly. Hopefully this doesn't cause random rare breakage.
I did not know that `std::optional::value()` did checked access. And I
still prefer a more explicit .has_value() over boolean conversion, but
this seems to be the accepted way to do this.
Robbert van der Helm