fix nil deference bugs and add tests

[ptrus]

This was already fixed in (recent) 22.1.x releases.

[codecov]

Codecov Report

Merging #4822 (368581c) into master (99af6b7) will decrease coverage by 0.15%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4822      +/-   ##
==========================================
- Coverage   66.71%   66.56%   -0.16%     
==========================================
  Files         451      451              
  Lines       50302    50307       +5     
==========================================
- Hits        33561    33488      -73     
- Misses      12588    12653      +65     
- Partials     4153     4166      +13     

Impacted Files	Coverage Δ
go/registry/api/api.go	57.42% <100.00%> (+1.03%)	⬆️
go/registry/api/runtime.go	49.09% <100.00%> (+1.15%)	⬆️
go/consensus/tendermint/abci/state/state.go	61.53% <0.00%> (-7.70%)	⬇️
go/runtime/host/sandbox/sandbox.go	60.82% <0.00%> (-6.53%)	⬇️
go/runtime/host/multi/multi.go	70.58% <0.00%> (-4.42%)	⬇️
go/worker/compute/executor/committee/node.go	69.22% <0.00%> (-4.06%)	⬇️
go/consensus/tendermint/full/light.go	61.53% <0.00%> (-3.85%)	⬇️
go/runtime/host/protocol/connection.go	68.42% <0.00%> (-3.76%)	⬇️
...consensus/tendermint/apps/roothash/transactions.go	66.66% <0.00%> (-3.12%)	⬇️
go/oasis-node/cmd/stake/delegations.go	78.99% <0.00%> (-1.69%)	⬇️
... and 21 more

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