Bug Report: segfault in StreamMigrator.identifyRuleType

[mvh-stripe]

Overview of the Issue

This issue is related to a previous fix: #9576
In the previous fix, the segfault was fixed in the code in Resharder. But the same bug also exists in the StreamMigrator.

2022-03-03T00:34:28.022066078Z stderr F I0303 00:34:28.021980       1 locks.go:214] Locking keyspace devmvhks26 for action SwitchWrites
2022-03-03T00:34:28.234463345Z stderr F I0303 00:34:28.234351       1 traffic_switcher.go:481] No previous journals were found. Proceeding normally.
2022-03-03T00:34:28.24433431Z stderr F I0303 00:34:28.244247       1 stream_migrator.go:763] found internal table _0d5669fe_9a86_11ec_8418_021fd2308fa7_20220303000829_vrepl, ignoring in rule identification
2022-03-03T00:34:28.244453719Z stderr F I0303 00:34:28.244401       1 traffic_switcher.go:492] Stopping streams
2022-03-03T00:34:28.246447989Z stderr F panic: runtime error: invalid memory address or nil pointer dereference
2022-03-03T00:34:28.246457813Z stderr F [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xf1a812]
2022-03-03T00:34:28.246463176Z stderr F
2022-03-03T00:34:28.246471758Z stderr F goroutine 422 [running]:
2022-03-03T00:34:28.246492528Z stderr F vitess.io/vitess/go/vt/vtctl/workflow.(*StreamMigrator).identifyRuleType(0xc0000ae210, 0xc000e822d0)
2022-03-03T00:34:28.246500321Z stderr F         vitess.io/vitess/go/vt/vtctl/workflow/stream_migrator.go:769 +0xf2
2022-03-03T00:34:28.246505908Z stderr F vitess.io/vitess/go/vt/vtctl/workflow.(*StreamMigrator).blsIsReference(0xc000002814, 0xc000e8c2c0)
2022-03-03T00:34:28.246531523Z stderr F         vitess.io/vitess/go/vt/vtctl/workflow/stream_migrator.go:735 +0x7c
2022-03-03T00:34:28.24654686Z stderr F vitess.io/vitess/go/vt/vtctl/workflow.(*StreamMigrator).readTabletStreams(0xc000cad320, {0x316d5b0, 0xc00058dfb0}, 0xc000cc5aa0, {0x2455c29, 0xc000573790})
2022-03-03T00:34:28.246555Z stderr F    vitess.io/vitess/go/vt/vtctl/workflow/stream_migrator.go:244 +0x57e
2022-03-03T00:34:28.246561045Z stderr F vitess.io/vitess/go/vt/vtctl/workflow.(*StreamMigrator).readSourceStreams.func1(0xc000bd66c0)
2022-03-03T00:34:28.246569723Z stderr F         vitess.io/vitess/go/vt/vtctl/workflow/stream_migrator.go:290 +0x9d
2022-03-03T00:34:28.246575389Z stderr F vitess.io/vitess/go/vt/wrangler.(*trafficSwitcher).ForAllSources.func1(0xc0009f41e0)
2022-03-03T00:34:28.246589316Z stderr F         vitess.io/vitess/go/vt/wrangler/traffic_switcher.go:134 +0x68
2022-03-03T00:34:28.246599591Z stderr F created by vitess.io/vitess/go/vt/wrangler.(*trafficSwitcher).ForAllSources
2022-03-03T00:34:28.246689954Z stderr F         vitess.io/vitess/go/vt/wrangler/traffic_switcher.go:131 +0xb1

Reproduction Steps

See https://github.com/vitessio/vitess/issues/9576

Binary Version

N/A

Operating System and Environment details

N/A

Log Fragments

No response