Make Safe version nullable

[hectorgomezv]

Problem
Validation errors are not being handled in the frontend. So when the service retrieves a Safe with a null version from the Transaction Service, the call to /chains/:chainId/safes/:safeAddress fails and the frontend is not capable of managing the error.

Failing when an incorrect Safe entity (with version: null) is retrieved is the correct behavior, but it's not the expected one right now.

Short-term solution

• Make version a nullable field for a Safe. The web UI already has some logic to manage null Safe versions: https://github.com/safe-global/safe-wallet-web/blob/consistent-provider/src/hooks/coreSDK/safeCoreSDK.ts#L56

Long-term solution

• Push the implementation of a validation error view in the clients, so they can manage this kind of scenario.

[hectorgomezv]

We've decided it's OK to fail on the CGW side for null versions since incorrect contract deployments (L2/nonL2 misalignment) won't be supported.

For special cases, the Safe Core team would add the contracts on demand.

[hectorgomezv]

Reopened as Safe{Core} team took the decision to make Safe version nullable. See: safe-global/safe-transaction-service#1571

[fmrsabino]

Reopened as Safe{Core} team took the decision to make Safe version nullable. See: safe-global/safe-transaction-service#1571

Since the version is already null on the API level I would say that we can move forward and remove this validation. The respective SDK also considers the version as null: https://github.com/safe-global/safe-gateway-typescript-sdk/blob/93dcd18a2738e5ccd30f803b9e39d55b9486210a/src/types/safe-info.ts#L20