server/storage/wal: fix oss-fuzz issue 44433

[AdamKorcz]

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=44433

[spzala]

Thanks @AdamKorcz It looks good to me but a small suggestion - considering multiple use of int(number) and enum.Values() it would be nice to create variables for them.

[serathius]

cc @ptabor @ahrtr

[codecov-commenter]

Codecov Report

Merging #13689 (674cc7c) into main (bba3937) will decrease coverage by 0.05%.
The diff coverage is 60.00%.

❗ Current head 674cc7c differs from pull request most recent head 0fcb2a6. Consider uploading reports for the commit 0fcb2a6 to get more accurate results

@@            Coverage Diff             @@
##             main   #13689      +/-   ##
==========================================
- Coverage   72.77%   72.72%   -0.06%     
==========================================
  Files         465      465              
  Lines       37865    37915      +50     
==========================================
+ Hits        27556    27573      +17     
- Misses       8535     8562      +27     
- Partials     1774     1780       +6     

Flag	Coverage Δ
all	72.72% <60.00%> (-0.06%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/storage/wal/version.go	52.76% <60.00%> (-0.07%)	⬇️
client/v3/txn.go	73.33% <0.00%> (-26.67%)	⬇️
raft/rafttest/node.go	95.00% <0.00%> (-5.00%)	⬇️
server/storage/mvcc/watchable_store.go	85.14% <0.00%> (-3.99%)	⬇️
server/etcdserver/api/v3election/election.go	66.66% <0.00%> (-2.78%)	⬇️
server/etcdserver/api/v3rpc/watch.go	85.90% <0.00%> (-2.02%)	⬇️
server/etcdserver/api/rafthttp/peer.go	85.06% <0.00%> (-1.95%)	⬇️
server/etcdserver/api/rafthttp/msgappv2_codec.go	71.30% <0.00%> (-1.74%)	⬇️
server/storage/mvcc/index.go	91.08% <0.00%> (-1.59%)	⬇️
server/storage/mvcc/kvstore_txn.go	75.27% <0.00%> (-1.10%)	⬇️
... and 12 more

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[spzala]

Thanks for addressing comments quickly @AdamKorcz