[BugFix] Fix NullPointerException in getTabletsInHighLoadPath when select tablets to balance (backport #51828)

[mergify]

Why I'm doing:

What I'm doing:

Fixes

2024-10-08 21:22:34.695+05:00 ERROR (tablet scheduler|68) [Daemon.run():109] daemon thread got exception. name: tablet scheduler
java.lang.NullPointerException: null
        at com.starrocks.clone.DiskAndTabletLoadReBalancer$BackendBalanceState.getTabletsInHighLoadPath(DiskAndTabletLoadReBalancer.java:2077) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.DiskAndTabletLoadReBalancer.balanceClusterDisk(DiskAndTabletLoadReBalancer.java:530) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.DiskAndTabletLoadReBalancer.selectAlternativeTabletsForCluster(DiskAndTabletLoadReBalancer.java:98) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.Rebalancer.selectAlternativeTablets(Rebalancer.java:67) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.TabletScheduler.selectTabletsForBalance(TabletScheduler.java:1557) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.TabletScheduler.runAfterCatalogReady(TabletScheduler.java:457) ~[starrocks-fe.jar:?]
        at com.starrocks.common.util.FrontendDaemon.runOneCycle(FrontendDaemon.java:72) ~[starrocks-fe.jar:?]
        at com.starrocks.common.util.Daemon.run(Daemon.java:107) ~[starrocks-fe.jar:?]

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
• This is a backport pr

Bugfix cherry-pick branch check:

• I have checked the version labels which the pr will be auto-backported to the target branch
  • 3.3
  • 3.2
  • 3.1
  • 3.0
  • 2.5

---

This is an automatic backport of pull request #51828 done by [Mergify](https://mergify.com). ## Why I'm doing:

What I'm doing:

Fixes

2024-10-08 21:22:34.695+05:00 ERROR (tablet scheduler|68) [Daemon.run():109] daemon thread got exception. name: tablet scheduler
java.lang.NullPointerException: null
        at com.starrocks.clone.DiskAndTabletLoadReBalancer$BackendBalanceState.getTabletsInHighLoadPath(DiskAndTabletLoadReBalancer.java:2077) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.DiskAndTabletLoadReBalancer.balanceClusterDisk(DiskAndTabletLoadReBalancer.java:530) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.DiskAndTabletLoadReBalancer.selectAlternativeTabletsForCluster(DiskAndTabletLoadReBalancer.java:98) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.Rebalancer.selectAlternativeTablets(Rebalancer.java:67) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.TabletScheduler.selectTabletsForBalance(TabletScheduler.java:1557) ~[starrocks-fe.jar:?]
        at com.starrocks.clone.TabletScheduler.runAfterCatalogReady(TabletScheduler.java:457) ~[starrocks-fe.jar:?]
        at com.starrocks.common.util.FrontendDaemon.runOneCycle(FrontendDaemon.java:72) ~[starrocks-fe.jar:?]
        at com.starrocks.common.util.Daemon.run(Daemon.java:107) ~[starrocks-fe.jar:?]

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
• This is a backport pr

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud