Some blocks are missing the bundle_type attribute

Here is what block query should look like (with bundle_type) returned:
```
$ curl https://blocks.flashbots.net/v1/blocks?block_number=14849437 | jq '.blocks[0].transactions[0]'
{
"transaction_hash": "0x3c265fa66e96365cd8b0aa974d482b10e392eacb095662b230bb02bf42016239",
"tx_index": 0,
"bundle_type": "flashbots", <-----------------------
"bundle_index": 0,
"block_number": 14849437,
"eoa_address": "0xD2006fcC22DF4a674839b357Ba1525cCb05efe92",
"to_address": "0x8aFF5cA996F77487a4f04F1ce905Bf3d27455580",
"gas_used": 131095,
"gas_price": "30969086989",
"coinbase_transfer": "4059892458912163",
"total_miner_reward": "4059892458912163",
"is_megabundle": true
}
```

Here's an example that is missing the "bundle_type" attribute, it's always on megabundle (but not all megabundles are missing it):
```
$ curl https://blocks.flashbots.net/v1/blocks?block_number=14849053 | jq '.blocks[0].transactions[0]'
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 6486 100 6486 0 0 15602 0 --:--:-- --:--:-- --:--:-- 15742
{
"transaction_hash": "0xb1a35fde6c36691e2d3185571616335490c5c7e65c7237ff9a151089115bb432",
"tx_index": 0,
"bundle_index": 0,
"block_number": 14849053,
"eoa_address": "0x881cd15C7c1aBF84416764fFbc6Dad44751122bb",
"to_address": "0x1111111254fb6c44bAC0beD2854e76F90643097d",
"gas_used": 180569,
"gas_price": "7000000000",
"coinbase_transfer": "0",
"total_miner_reward": "1263983000000000",
"is_megabundle": true
}