expression: fix substring_index crash tiflash in some case

[wshwsh12]

What problem does this PR solve?

Issue Number: close #9116

Problem Summary:

What is changed and how it works?

Fix tiflash crash caused by function `substring_index` in some corner cases

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 tiflash crash caused by function `substring_index` in some corner cases

[windtalker]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-11 08:21:06.073455064 +0000 UTC m=+452820.126766987: ☑️ agreed by windtalker.
• 2024-06-11 08:26:12.780667263 +0000 UTC m=+453126.833979189: ☑️ agreed by solotzg.

[JaySon-Huang]

We'd better add assert(count != 0); after line 5214, or it may cause something wrong when it comes to the following branch with count == 0

tiflash/dbms/src/Functions/FunctionsString.cpp

Lines 5258 to 5263 in fce582b

	if (count <= static_cast<Int64>(delim_pos.size()))
	{
	auto delim_count = delim_pos.size();
	const UInt8 * match = delim_pos[delim_count - count];
	begin = match + delim_size;
	}

It is OK for now because count == 0 has some shortcuts in the upper level.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JaySon-Huang, solotzg, windtalker

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #9139.

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In response to a cherrypick label: new pull request created to branch release-7.5: #9140.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #9141.

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In response to a cherrypick label: new pull request created to branch release-8.1: #9142.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.1: #9143.

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In response to a cherrypick label: new pull request created to branch release-5.4: #9144.