Return proper value for logsBloom field on block endpoints

[m-Peter]

The following error was reported:

Deserialization Error: invalid length 0, expected a (both 0x-prefixed or not) hex string or byte array containing 256 bytes at line 1 column 303. Response: 
{"number":"0x935","hash":"0x378891ccb8befad477156a3272f9bde017c98cdb3770075b1887d3baeab0165f","parentHash":"0x18c13daacf83338a667c466ca978db2dc1c89423233c4e66b3af36d10bb49542","nonce":"0x0100000000000000","sha3Uncles":"0x0000000000000000000000000000000000000000000000000000000000000000","logsBloom":"0x","transactionsRoot":"0x0000000000000000000000000000000000000000000000000000000000000000","stateRoot":"0x0000000000000000000000000000000000000000000000000000000000000000","receiptsRoot":"0x0000000000000000000000000000000000000000000000000000000000000000","miner":"0x0000000000000000000000000000000000000000","difficulty":"0x0","totalDifficulty":"0x0","extraData":"0x","size":"0x0","gasLimit":"0xe4e1c0","gasUsed":"0x4bfa1","timestamp":"0x0","transactions":["0xced13a966936bb80e65ac99112e0f12836a05e571cb7910642496cb840255190"],"uncles":[],"mixHash":"0x0000000000000000000000000000000000000000000000000000000000000000"}