Panic on load from immutable DB

[agaffney]

I ran into this on a local dingo run in preview when the data dir was still populated from a previous run, and the local tip was later than the immutable DB tip.

{"time":"2025-09-11T20:02:09.072050665Z","level":"INFO","msg":"copying blocks from immutable DB"}
panic: runtime error: index out of range [18193] with length 18193

goroutine 1 [running]:
github.com/blinklabs-io/dingo/database/immutable.(*ImmutableDb).getChunkNamesFromPoint(0xc0068aa300, {{}, 0x0?, {0xc00681f100?, 0x0?, 0x56c0356?}})
        /home/agaffney/dev/blinklabs-io/dingo/database/immutable/immutable.go:85 +0x20e
github.com/blinklabs-io/dingo/database/immutable.(*ImmutableDb).BlocksFromPoint(0xc0068aa300, {{}, 0x241d688?, {0xc00681f100?, 0x0?, 0x20317fa?}})
        /home/agaffney/dev/blinklabs-io/dingo/database/immutable/immutable.go:274 +0x38

The failing line is here:

dingo/database/immutable/immutable.go

Line 85 in 2ab6fbb

middleChunkName := chunkNames[middlePoint]