Sounds fishy to me. MidiLEDHandler needing an overhaul notwithstanding, it shouldn't be appearing at all if no MIDI controller is attached! My guess is that mappings stored in .mixxx/midi/ are being loaded anyway. Jus, can you check to see if there are files in there and delete them if so, test again, and get another gprof output?
Sounds fishy to me. MidiLEDHandler needing an overhaul notwithstanding, it shouldn't be appearing at all if no MIDI controller is attached! My guess is that mappings stored in .mixxx/midi/ are being loaded anyway. Jus, can you check to see if there are files in there and delete them if so, test again, and get another gprof output?