Add guards to other pane index removals (#2496)

These should be impossible for users to reach, but why leave it to
chance?

Release Notes:

* N/A

Mikayla Maki committed 3y ago

06a89d9104b232de2a1fe2fc2b2d3d7c6b21ad56

Committed by GitHub <noreply@github.com> on 5/19/2023, 10:21:00 PM