minor mutable-state log fix

[davidporter-id-au]

What changed?
Some reasonable feedback on a diff I didn't address before autolanding, so landing here. Just making the logs both slightly more defensive and returning early where possible.

Why?

How did you test it?

Potential risks

Release notes

Documentation Changes

[coveralls]

Pull Request Test Coverage Report for Build 018e2f31-f624-46df-bca7-f24f826c6a82

Details

• 9 of 15 (60.0%) changed or added relevant lines in 1 file are covered.
• 49 unchanged lines in 10 files lost coverage.
• Overall coverage increased (+0.02%) to 64.1%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
service/history/execution/mutable_state_builder.go	9	15	60.0%

Files with Coverage Reduction	New Missed Lines	%
service/history/task/transfer_standby_task_executor.go	2	87.01%
common/persistence/sql/sqlplugin/postgres/task.go	2	73.4%
common/persistence/sql/sqlplugin/postgres/db.go	2	80.0%
service/matching/taskListManager.go	2	79.7%
service/history/queue/timer_queue_processor_base.go	3	77.82%
common/persistence/statsComputer.go	3	94.64%
service/frontend/wrappers/metered/metered.go	4	65.5%
service/history/execution/mutable_state_task_refresher.go	7	66.46%
service/history/execution/mutable_state_builder.go	12	70.3%
common/persistence/sql/workflow_state_maps.go	12	81.25%

Totals
Change from base Build 018e2ebe-807b-4e78-97fa-f22e8f0a52db:	0.02%
Covered Lines:	93452
Relevant Lines:	145791

---

💛 - Coveralls