Describe the problem

In #61541 (comment), we saw that a range with an uninitialized follower transferred the lease to that uninitialized follower, leading to the range becoming unavailable until the follower caught up. This indicates a hole in our safety mechanisms.

To Reproduce

Unclear, but the test in #61541 definitely achieved it.

Expected behavior
A clear and concise description of what you expected to happen.

Additional data / screenshots

Environment:

https://github.com/cockroachdb/cockroach/commits/b703e663da8ededaee2e28fc39a24e3880ae54cf

Additional context

It looks like aggressive changes in range size can lead to temporary (but substantial) unavailability.

gz#9425