fix: machine locator error handling prevents nil dereference

[joshuacolvin0]

Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com

[codecov]

Codecov Report

❌ Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 31.97%. Comparing base (b9d1452) to head (af84ef3).
⚠️ Report is 30 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4530      +/-   ##
==========================================
- Coverage   32.67%   31.97%   -0.70%     
==========================================
  Files         497      497              
  Lines       58849    58851       +2     
==========================================
- Hits        19227    18820     -407     
- Misses      36245    36638     +393     
- Partials     3377     3393      +16     

[github-actions]

❌ 9 Tests Failed:

Tests completed	Failed	Passed	Skipped
4501	9	4492	0

View the top 3 failed tests by shortest run time

TestPruningDBSizeReduction

Stack Traces | 0.000s run time

=== RUN   TestPruningDBSizeReduction
--- FAIL: TestPruningDBSizeReduction (0.00s)

TestAnyTrustRekey

Stack Traces | 13.900s run time

... [CONTENT TRUNCATED: Keeping last 20 lines]
INFO [03-19|15:22:24.863] Loaded most recent local block           number=0   hash=900eda..256170 age=57y1w4d
INFO [03-19|15:22:24.864] Initialized transaction indexer          range="last 126230400 blocks"
INFO [03-19|15:22:24.864] Updated payload                          id=0x03fc8c1211c04206 number=4   hash=1fa471..2bd070 txs=1   withdrawals=0 gas=3,188,091  fees=3.188091e-06   root=11dbe5..9df12a elapsed=12.260ms
        github.com/offchainlabs/nitro/system_tests.Require(0xc000402700, {0x47a7f80, 0xc09a35d410}, {0xc01736d120, 0x1, 0x1})
        	/home/runner/work/nitro/nitro/system_tests/common_test.go:2094 +0x5d
        github.com/offchainlabs/nitro/system_tests.(*NodeBuilder).BuildL2OnL1(0xc000598240, 0xc000402700)
        	/home/runner/work/nitro/nitro/system_tests/common_test.go:944 +0x5ae
        github.com/offchainlabs/nitro/system_tests.TestAnyTrustRekey(0xc000402700)
        	/home/runner/work/nitro/nitro/system_tests/anytrust_test.go:162 +0xf2a
        testing.tRunner(0xc000402700, 0x4418ed8)
        	/opt/hostedtoolcache/go/1.25.8/x64/src/testing/testing.go:1934 +0xea
        created by testing.(*T).Run in goroutine 1
        	/opt/hostedtoolcache/go/1.25.8/x64/src/testing/testing.go:1997 +0x465
        
    common_test.go:944: �[31;1m [failed to deploy ArbDebug] nonce too low: address 0x26E554a8acF9003b83495c7f45F06edCB803d4e3, tx: 0 state: 2 �[0;0m
INFO [03-19|15:22:24.833] Stopping work on payload                 id=0x030aa56f03de0831 reason=delivery
INFO [03-19|15:22:24.834] Imported new potential chain segment     number=44  hash=33f915..843656 blocks=1  txs=0   mgas=0.000  elapsed=4.447ms     mgasps=0.000    triediffs=218.27KiB triedirty=0.00B
--- FAIL: TestAnyTrustRekey (13.90s)
INFO [03-19|15:22:24.869] Chain head was updated                   number=44  hash=33f915..843656 root=81e9db..148e3e elapsed="182.247µs"
INFO [03-19|15:22:24.846] New Key                                  name=CleanBeneficiary    Address=0x758fA62a2e12584aa7857d4221dC7BB174009b45

TestStakersCooperative

Stack Traces | 19.740s run time

... [CONTENT TRUNCATED: Keeping last 20 lines]
DEBUG[03-19|15:15:58.190] Journaled pathdb diff layer              root=49ca06..6b9a6e parent=a21648..beddf1 id=511                block=510
DEBUG[03-19|15:15:58.190] Journaled pathdb diff layer              root=3e7863..de3184 parent=49ca06..6b9a6e id=512                block=511
DEBUG[03-19|15:15:58.190] Journaled pathdb diff layer              root=6094fd..6dd0fe parent=3e7863..de3184 id=513                block=512
DEBUG[03-19|15:15:58.190] Journaled pathdb diff layer              root=c3deb2..6b99a2 parent=6094fd..6dd0fe id=514                block=513
DEBUG[03-19|15:15:58.190] Journaled pathdb diff layer              root=40a582..23af2c parent=c3deb2..6b99a2 id=515                block=514
DEBUG[03-19|15:15:58.190] Journaled pathdb diff layer              root=338010..93009d parent=40a582..23af2c id=516                block=515
DEBUG[03-19|15:15:58.190] Journaled pathdb diff layer              root=641f45..ea6c8f parent=338010..93009d id=517                block=516
DEBUG[03-19|15:15:58.191] Journaled pathdb diff layer              root=cf206b..f04531 parent=641f45..ea6c8f id=518                block=517
INFO [03-19|15:15:58.191] Persisted dirty state to disk            size=1002.69KiB elapsed=16.339ms
INFO [03-19|15:15:58.192] Blockchain stopped
TRACE[03-19|15:15:58.192] P2P networking is spinning down
DEBUG[03-19|15:15:58.192] RPC server shutting down
DEBUG[03-19|15:15:58.192] RPC connection read error                err="read tcp 127.0.0.1:37207->127.0.0.1:58972: use of closed network connection"
DEBUG[03-19|15:15:58.193] RPC connection read error                err="websocket: close 1006 (abnormal closure): unexpected EOF"
DEBUG[03-19|15:15:58.193] RPC connection read error                err="websocket: close 1006 (abnormal closure): unexpected EOF"
DEBUG[03-19|15:15:58.193] RPC connection read error                err="read tcp 127.0.0.1:37207->127.0.0.1:58986: use of closed network connection"
INFO [03-19|15:15:58.193] HTTP server stopped                      endpoint=127.0.0.1:37207
DEBUG[03-19|15:15:58.193] RPC server shutting down
TRACE[03-19|15:15:58.193] P2P networking is spinning down
--- FAIL: TestStakersCooperative (19.74s)

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[KolbyML]

looks good