Fix persistent storage startup with blank initialBuckets entries

[VAdaihiep]

Description
This PR fixes a startup bug in persistent storage mode where a blank initialBuckets entry could create an invalid root-level persisted bucket metadata file and cause InternalError responses after restart.

Changes:

• Ignore blank or whitespace-only initialBuckets entries during startup.
• Add a regression test covering initialBuckets = listOf("").
• Update CHANGELOG.md with the bug fix.

Related Issue

• N/A

Tasks

• I have written tests and verified that they fail without my change.
• I have run make format to fix code style.
• I have updated CHANGELOG.md (if applicable).
• I have updated documentation (if applicable).
• I have signed the CLA.
  • Nếu bạn đã ký rồi thì tick luôn ô này trước khi mở PR.

Verification

• Ran:

  .\mvnw.cmd -B -V -pl server -Dtest=StoreConfigurationTest test

• Result: test suite passed.