Error when saving an entry when Structure isn't set up for this site.

[boilerroomdigital]

Description of the problem
We have a system with four MSM sites. Some use Structure, some don't. On saving an entry where Structure isn't set up I get the following error:

Deprecated

base64_decode(): Passing null to parameter #1 ($string) of type string is deprecated

ee/ExpressionEngine/Addons/structure/sql.structure.php, line 1437

Severity: E_DEPRECATED

The entry still saves but the success screen isn't shown, instead the error blocks the output.

Environment Details:

• Version: 7.5.7
• PHP Version 8.3.19
• MySQL Version 5.7.42
• OS: Linux
• Web Server: Apache

Possible Solution
Replace line 1437 of sql.structure.php with the following:

if(is_string($pages_array))
{
		$all_pages = unserialize(base64_decode($pages_array['site_pages']));
}
else
{
	$all_pages = array();
}

There could be a better solution, but this seems to work for me.

Additional context
Our site has been updated from Version 2 via intermediate versions, so it's possible that this is the source of the issue.

[TomJaeger]

Thanks for submitting this.

After testing, it looks like this is likely due to data being or not being present in the DB that should by default.

It's likely we should catch that case.. but also confirm whats in the DB is whats expected.