This was a regression with my recent fixes to pinned tabs. Dragging a
pinned tab left in the pinned region would still update the pinned tab
count, which would later cause an out-of-bounds later when it used that
value to index into a vec.

https://zed-industries.slack.com/archives/C04S6T1T7TQ/p1749220447796559

Release Notes:

- Fixed a panic caused by dragging a pinned item to the left in the
pinned region