fix warning when open xlsx file with thumbnail

[mix5003]

This is:

- [x] a bugfix
- [ ] a new feature

Checklist:

• Changes are covered by unit tests
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change
• Documentation is updated as necessary

Why this change is needed?

this should fix #2516. by not try to open thumbnail as xml

[oleibman]

Your test file is very large, and I am having trouble reading it because of that, but not because of the thumbnail file. I am going to upload another, much smaller file. Do you see the same warning message when you read it? I don't see any warning messages with several different versions of PhpSpreadsheet. I do see a bit of a problem - the thumbnail fail is basically ignored rather than used when, for example, saving a copy of the original - but that's a different problem that will need a different solution.
issue.2516b.xlsx

[mix5003]

i updated test files.

I don't see any warning messages with several different versions of PhpSpreadsheet

it should show warning because this piece of code try to call loadZip every files in _rels/.rels link

PhpSpreadsheet/src/PhpSpreadsheet/Reader/Xlsx.php

Lines 175 to 190 in aa29947

	$rels = $this->loadZip(self::INITIAL_FILE, Namespaces::RELATIONSHIPS);
	foreach ($rels->Relationship as $relx) {
	$rel = self::getAttributes($relx);
	$relType = (string) $rel['Type'];
	$mainNS = self::REL_TO_MAIN[$relType] ?? Namespaces::MAIN;
	if ($mainNS !== '') {
	$xmlWorkbook = $this->loadZip((string) $rel['Target'], $mainNS);
	if ($xmlWorkbook->sheets) {
	foreach ($xmlWorkbook->sheets->sheet as $eleSheet) {
	// Check if sheet should be skipped
	$worksheetNames[] = (string) self::getAttributes($eleSheet)['name'];
	}
	}
	}
	}

and loadZip try to open it as XML

PhpSpreadsheet/src/PhpSpreadsheet/Reader/Xlsx.php

Lines 122 to 133 in aa29947

	private function loadZip(string $filename, string $ns = ''): SimpleXMLElement
	{
	$contents = $this->getFromZipArchive($this->zip, $filename);
	$rels = simplexml_load_string(
	$this->securityScanner->scan($contents),
	'SimpleXMLElement',
	Settings::getLibXmlLoaderOptions(),
	$ns
	);
	return self::testSimpleXml($rels);
	}

in this case docProps/thumbnail.wmf is not xml. so it should warning like my original issue
simplexml_load_string(): Entity: line 1: parser error : Start tag expected, '<' not found

but if you don't see warning message i think it up to default error_reporting level. if default error_reporting is E_ERROR (not show warning). it will not show anything. should i add error_reporting(E_WARNING); in test case? or do you have anyway to test it properly?

[oleibman]

Aha! Thank you for the explanation. The warning messages you see are when you execute the listWorksheetNames method, and I didn't see them because I was executing the load method. It seems to me that the listWorksheetInfo method should have the same problem as listWorksheetNames, and that your fix for one should also fix the other. Can you please add an additional test for listWorksheetInfo?

[mix5003]

added test for listWorksheetInfo

[oleibman]

Thank you for your contribution.