[zeditor] crash-to-desktop in Debug mode when playing Wind Fish ambient music

Steps to recreate:

1. Open ZeldaClassic.sln in Microsoft Visual Studio
2. Set a breakpoint at the { of body of playTune(int32_t) in zquest.cpp
3. F5 (Debug->Start Debugging)
4. Etc->Media->Ambient Music->Wind Fish
5. F5 (Debug->Continue)
6. ASSERT(new_speed_secs > 0); fails in al_set_timer_speed

Wind Fish plays in release builds.