bug: Madara fails to sync block 20732 because of Legacy contract deserialization

[notlesh]

Is there an existing issue?

• I have searched the existing issues

Description of bug

While trying to sync mainnet with Madara, I found that sync fails on block 20732 when it attempts to request class 0x371b5f7c5517d84205365a87f02dcef230efa7b4dd91a9e4ba7e04c5b69d69b.

Error (not very helpful):

The provider has returned an error: Error serializing request: invalid type: null, expected a sequence, retrying in 6s

Specifically, it fails when trying to convert to a LegacyContractClass via serde_json::from_value here.

If we print the value it's attempting to use, we see that it has a null for abi:

{"abi":null,"entry_points_by_type":{"CONSTRUCTOR" ...

Which I'm guessing is why it fails.

Steps to reproduce

Sync mainnet with Madara up to block 20732, e.g.:

cargo run --release \
    -- \
    --name Madara \
    --full \
    --base-path "../somewhere" \
    --network mainnet \
    --l1-endpoint "<redacted>"

[antiyro]

This PR should solve it #394. Tell me if it works.