fix: fix null protocol version error (#2094)

## What ❔

Don't return results with NULL protocol version from DB.

## Why ❔

It's incorrect

## Checklist

<!-- Check your PR fulfills the following items. -->
<!-- For draft PRs check the boxes as you complete them. -->

- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [x] Tests for the changes have been added / updated.
- [x] Documentation comments have been added / updated.
- [x] Code has been formatted via `zk fmt` and `zk lint`.
- [x] Spellcheck has been run via `zk spellcheck`.

prover/prover_dal/src/fri_proof_compressor_dal.rs

@@ -266,6 +266,8 @@ impl FriProofCompressorDal<'_, '_> {
                 ) AS in_progress
             FROM
                 proof_compression_jobs_fri
+            WHERE
+                protocol_version IS NOT NULL
             GROUP BY
                 status,
                 protocol_version