Fix: AfterChunk event raised after sheet disconnect

[zigzagdev]

1️⃣Why should it be added? What are the benefits of this change?

AfterChunk was fired after Sheet::disconnect() in ReadChunk::handle().
disconnect() calls unset($this->worksheet), so any event handler that accesses $event->getSheet()->getDelegate() would encounter an undefined property and receive null instead of the expected Worksheet instance.
Moving raise(AfterChunk) before disconnect() ensures the worksheet is still accessible inside event handlers, which is the naturally expected behavior.

2️⃣Does it contain multiple, unrelated changes?

No.
This PR contains a single focused fix: reordering raise(AfterChunk) and disconnect() in ReadChunk::handle().

3️⃣Does it include tests, if possible?

Yes.
test_after_chunk_event_sheet_delegate_is_accessible has been added to WithEventsTest, asserting that $event->getSheet()->getDelegate() returns a Worksheet instance within an AfterChunk handler.

4️⃣Any drawbacks? Possible breaking changes?

No breaking changes.
The fix only corrects the order of two operations. Event handlers that do not access getDelegate() are unaffected.

5️⃣Tasks

• Checked the codebase to ensure that your feature doesn't already exist.
• Take note of the contributing guidelines.
• Checked the pull requests to ensure that another person hasn't already submitted a fix.
• Added tests to ensure against regression.

Test Results

[patrickbrouwers]

can you retarget this to 4.x

[zigzagdev]

@patrickbrouwers

can you retarget this to 4.x

I changed target branch. So please check my PR.

[AJenbo]

NIT: raise can throw so just in case it does it could be best to make sure the disconnect and cleanup still happens.

Suggested change

	$sheet->raise(new AfterChunk($sheet, $this->import, $this->startRow));
	$sheet->disconnect();
	$this->cleanUpTempFile();
	try {
	$sheet->raise(new AfterChunk($sheet, $this->import, $this->startRow));
	} finally {
	$sheet->disconnect();
	$this->cleanUpTempFile();
	}