tools: pingpong nil fix

[brianolson]

Summary

nil-hash-write bug fix

Test Plan

Found in testing. Later manual testing is better.

[codecov]

Codecov Report

Merging #4558 (3551b6e) into master (7e8ca90) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #4558      +/-   ##
==========================================
- Coverage   54.11%   54.07%   -0.05%     
==========================================
  Files         401      401              
  Lines       51549    51551       +2     
==========================================
- Hits        27898    27877      -21     
- Misses      21311    21327      +16     
- Partials     2340     2347       +7     

Impacted Files	Coverage Δ
shared/pingpong/accounts.go	3.40% <0.00%> (-0.02%)	⬇️
ledger/roundlru.go	90.56% <0.00%> (-5.67%)	⬇️
cmd/algoh/blockWatcher.go	77.77% <0.00%> (-3.18%)	⬇️
network/wsPeer.go	68.19% <0.00%> (-2.70%)	⬇️
crypto/merkletrie/trie.go	66.42% <0.00%> (-2.19%)	⬇️
crypto/merkletrie/node.go	91.62% <0.00%> (-1.87%)	⬇️
network/wsNetwork.go	64.63% <0.00%> (-0.20%)	⬇️
catchup/service.go	69.38% <0.00%> (+0.74%)	⬆️

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