Fix empty track issue

[buraksenkus]

Description

The changes in this pull request fixes empty track issue in _midi_file object is midigen.py.

Fixes #24

Changes and Fixes

• I've added a new feature (provide details).
• I've fixed a bug (give a brief explanation of how it was resolved).
• I've made a breaking change (describe what was changed).
• I've made an enhancement to an existing feature (describe what was enhanced).

I've removed _track object and used self.midi_file.tracks[0] reference to avoid redundant track store.

How Has This Been Tested?

I've written test_tracks function in test_midigen.py to test my fix. Other tests also pass successfully.

Checklist:

• My code follows the code style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in areas that may be hard for others to understand.
• I have updated the documentation to reflect my changes.
• My changes do not generate new warnings.
• I have added tests that prove my changes are effective.
• New and existing unit tests pass locally with my changes.

[cainky]

Hello @buraksenkus, thank you very much for your pull request! I was quite pleasantly surprised to see your comments – it is really great to know that others find interest in my repo

I deeply appreciate your initiative in identifying and addressing the issue. Rest assured, I'll review your pull request thoroughly and ensure any necessary fixes are implemented promptly. It's exciting to hear that you plan to use this library in your personal project, and your periodic contributions are most welcome.

Thanks again for your valuable input and support

[cainky]

I can work with this! :)