[UT] [BugFix] Fix possible NPE querying task_runs schema table (backport #55968)

[mergify]

Why I'm doing:

 2025-02-11 15:04:24.414+08:00 ERROR (thrift-server-pool-125|2590) [ProcessFunction.process():49] Internal error processing getTaskRuns
 java.lang.NullPointerException: Cannot invoke "com.starrocks.load.loadv2.InsertLoadJob.getProgress()" because "job" is null
        at com.starrocks.scheduler.TaskRun.getStatus(TaskRun.java:326)
        at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
        at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
        at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1845)
        at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
        at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
        at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
        at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
        at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
        at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596)
        at com.starrocks.scheduler.TaskManager.getMatchedTaskRunStatus(TaskManager.java:615)
        at com.starrocks.catalog.system.information.TaskRunsSystemTable.query(TaskRunsSystemTable.java:192)
        at com.starrocks.service.FrontendServiceImpl.getTaskRuns(FrontendServiceImpl.java:886)
        at com.starrocks.thrift.FrontendService$Processor$getTaskRuns.getResult(FrontendService.java:5617)
        at com.starrocks.thrift.FrontendService$Processor$getTaskRuns.getResult(FrontendService.java:5594)
        at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:40)
        at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:40)
        at com.starrocks.common.SRTThreadPoolServer$WorkerProcess.run(SRTThreadPoolServer.java:311)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
        at java.base/java.lang.Thread.run(Thread.java:840)

What I'm doing:

• Avoid NPE in getTaskRunStatus

Fixes https://github.com/StarRocks/StarRocksTest/issues/9219

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

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

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

See analysis details on SonarQube Cloud