ddl: fix cleanup subtasks after cancel add index with dist-reorg

[zimulala]

What problem does this PR solve?

Issue Number: close #41371

Problem Summary:

What is changed and how it works?

Do cleanupBackfillJobs after canceling the operation.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• Defined2014
• hawkingrei

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[hawkingrei]

@zimulala I found it in the CI.

panic: runtime error: invalid memory address or nil pointer dereference

[signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x448b259]


goroutine 183764 [running]:

github.com/pingcap/tidb/ddl.(*reorgCtx).isReorgCanceled(...)

	ddl/reorg.go:113

github.com/pingcap/tidb/ddl.(*reorgCtx).IsReorgCanceled(...)

	ddl/ddl_test.go:62

github.com/pingcap/tidb/ddl_test.TestUsingReorgCtx.func2()

	ddl/ddl_worker_test.go:334 +0xd9

github.com/pingcap/tidb/util.(*WaitGroupWrapper).Run.func1()

	util/wait_group_wrapper.go:154 +0x6b

created by github.com/pingcap/tidb/util.(*WaitGroupWrapper).Run

	util/wait_group_wrapper.go:152 +0x8d

--

Coverage runner: Not collecting coverage for failed test.

[zimulala]

@zimulala I found it in the CI.

panic: runtime error: invalid memory address or nil pointer dereference

[signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x448b259] ...

@hawkingrei
This may be an unstable test or a bug, but it doesn't because of this PR. I will handle it. Could you add an issue?

[zimulala]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 3b103e0