Added
- debug messages in converters
Fixed
- converters/EventToMidiFile: Fix crash if extractor returns None (see [here](https://github.com/mutwo-org/mutwo.midi/commit/8818873b40133163436c709a66fde778bf376ab0))
- converters/EventToMidiFile: Fix crash for empty Sim[Seq, ...] (see [here](https://github.com/mutwo-org/mutwo.midi/commit/4802bf133f423451842b27ba747c1766e54908fd))