Error handling for missing deposit proposal

[sifnoc]

There is slashable proposal block(#3442) on goerli testnet which only has massDeposit without any deposit.
I was wrong, #3442 is valid block. the coordinator overwritten deposit notes in the database due to some malicious deposit transactions.

so, the coordinator throw error like below when processing blocks
checkSubmittedDeposits

core/fullnode-validator - offchain validation error: validateUTXOIndex([{\"hash\":\"0x26f5eabd25f520f36fa549d35f4dac
7b419e317c0f7ee34a84102632ca0bd7e4\",\"slashed\":false,\"header\":{\"proposer\":\"0x526577e9Ec39000df24aCba07d08EC35DCEa39C5\",\"parentBlock\":\"0x8ddc285172b9fb15f07125ef85c8bf22bc3646621b6
c3f1af3eaf06c1131a5dc\",\"fee\":\"2399999000000000\",\"utxoRoot\":\"13027746520285120230260551090469112361816809969536613413366601539612571046517\",\"utxoIndex\":\"113056\",\"nullifierRoot\"
:\"0x1e60b0078106fb37a738a41702d7804253e46f383a070e3513af37bc37aece7b\",\"withdrawalRoot\":\"3686835620964389061533172228241702054413900201285875732653541605255963102001\",\"withdrawalIndex\
":\"9120\",\"txRoot\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"depositRoot\":\"0xdd78f9f611258824de51fc49bb5bd43ed0cf4200d24da24cae750e236431fd28\",\"migratio
nRoot\":\"0x0000000000000000000000000000000000000000000000000000000000000000\"},\"body\":{\"txs\":[],\"massDeposits\":[{\"merged\":\"0xff0dd5bf878657a3b33bf947cda9eb57c38e8da080f52976b2c2366
e6ca1d01f\",\"fee\":\"2399999000000000\"}],\"massMigrations\":[]}},{\"proposer\":\"0x526577e9Ec39000df24aCba07d08EC35DCEa39C5\",\"parentBlock\":\"0x6303b7cc049fa03792d26b34a38edcb895f4f7a5ea
953ace678c203d61f62e90\",\"fee\":\"4799999000000000\",\"utxoRoot\":\"10150135194032801411551506389403053941638565303478370133934367641156854134123\",\"utxoIndex\":\"113024\",\"nullifierRoot\
":\"0x1e60b0078106fb37a738a41702d7804253e46f383a070e3513af37bc37aece7b\",\"withdrawalRoot\":\"3686835620964389061533172228241702054413900201285875732653541605255963102001\",\"withdrawalIndex
\":\"9120\",\"txRoot\":\"0x0000000000000000000000000000000000000000000000000000000000000000\",\"depositRoot\":\"0x714643de19fb2f385582fab25c06643392ee1e8977cdb8e0270830feb8d90bd8\",\"migrati
onRoot\":\"0x0000000000000000000000000000000000000000000000000000000000000000\"},[]]): TypeError: Cannot read properties of undefined (reading 'toBytes')

validateUTXOIndex and validateUTXORoot are skip by these error.

But this slashable block invalid at validateMassDeposit eventually.