app: (*SommelierApp).prepForZeroHeightGenesis should instead use a defer iter.Close() to ensure that the store gets closed on any panic

[odeke-em]

Summary of Bug

Given the usage of panics down below in this code section

sommelier/app/export.go

Lines 155 to 174 in 3157d97

	iter := sdk.KVStoreReversePrefixIterator(store, stakingtypes.ValidatorsKey)
	counter := int16(0)
	for ; iter.Valid(); iter.Next() {
	addr := sdk.ValAddress(iter.Key()[1:])
	validator, found := app.StakingKeeper.GetValidator(ctx, addr)
	if !found {
	panic("expected validator, not found")
	}
	validator.UnbondingHeight = 0
	if applyAllowedAddrs && !allowedAddrsMap[addr.String()] {
	validator.Jailed = true
	}
	app.StakingKeeper.SetValidator(ctx, validator)
	counter++
	}
	iter.Close()

, despite having an iter.Close() down at Line 174, it is important to use defer iter.Close() which will allow for clean up by closing the store and releasing resources