Problem Definition

When a precommit messsge is received, VerifyVoteExtension is called even if the message does not have an extension or the extension has length 0, according to the current version of the ABCI++ spec

The question is whether is would make sense to skip the verification in the case of empty or non-existent extension. This probably depends on the use cases for vote extensions. Currently we don't see an obvious reason not skip the verification under such conditions.

Once a decision is reached, we need to adapt the implementation (should be quick). Also, the spec should be updated to clearly describe the approach described (probably in section "When does Tendermint use it")

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