Empty TCO still acts like BB editor on high zoom

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### System Information

Windows 11

### LMMS Version(s)

1.3.0-alpha.1.780+9159533 (win32/x86_64, Qt 5.15.16, GCC 14.2.0).

### Most Recent Working Version

_No response_

### Bug Summary

After #5988, the B/B editor object is no longer drawn by default on an empty piano roll TCO at high zoom levels.
However, if the TCO is highly zoomed in, _scrolling_ over this empty TCO still creates Stepnotes just like scrolling over a B/B tombstone would.

### Expected Behaviour

There is no effect; LMMS scrolls over the tracklist like it should do normally.

### Steps To Reproduce

1. Create empty piano roll TCO
2. Check at the default zoom level or zoom in
3. Scroll mouse wheel upward while hovering over TCO
4. See zero-length note appear. Its volume can be adjusted by scrolling too.

### Logs

### Screenshots / Minimum Reproducible Project

https://github.com/user-attachments/assets/0a84127e-c1c8-48a3-a601-0efd37878d8e

### Please search the issue tracker for existing bug reports before submitting your own.

- [x] I have searched all existing issues and confirmed that this is not a duplicate.

Reproduce the issue with an empty piano roll TCO at default and high zoom, then inspect the mouse-wheel handling for the TCO and the B/B editor object. Done means scrolling over the empty TCO has no effect and does not create or adjust a zero-length note, while normal tracklist scrolling still works.

Written by the indexing model from the issue text.