PageStorage: Fix an exception in gc when meet an empty WriteBatch

[JaySon-Huang]

What problem does this PR solve?

Issue Number: close #10401

Problem Summary:

In the previous code, if the last WriteBatch contains no changes is persisted in the LogFile, then it may lead to exception in getMaxSequenceForRecord as the issue describe.

What is changed and how it works?

PageStorage: Fix an exception in gc when meet an empty WriteBatch
* If the last edit stored in Logfile is empty, then we won't collect that LogFile for compacting WAL in the current GC round
* These remain log_files will be compacted in the following rounds once we found a log_file has larger log_num and its max_seq <= snap_sequence.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Fix an exception that may block data from being GCed

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JinheLin, Lloyd-Pottiger

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-09-05 01:52:56.532365903 +0000 UTC m=+144720.515463341: ☑️ agreed by Lloyd-Pottiger.
• 2025-09-05 02:35:15.052535014 +0000 UTC m=+147259.035632492: ☑️ agreed by JinheLin.