voyager: handle partially pruned state

[benluelo]

code=38
log=failed to load state at height 3724044; version mismatch on immutable IAVL tree; version does not exist. Version has either been pruned, or is for a future block height (latest height: 3883336): not found
info=
index=0
key=None
value=None
height=0
codespace=sdk
proof_ops=None

this should be handled correctly, currently we just kinda explode