Fixes #3394 PHP notice in Update_Subscriber::disable_auto_updates()

[NataliaDrause]

Description

Adds guard close isset() to prevent the PHP notice, by checking if the property is set before using it.
Fixes #3394

Type of change

• Bug fix (non-breaking change which fixes an issue)

Is the solution different from the one proposed during the grooming?

No

How Has This Been Tested?

The issue was reproduced by adding
unset($item->plugin);
under this line:

wp-rocket/inc/classes/subscriber/Plugin/class-updater-subscriber.php

Line 270 in f403aa5

public function disable_auto_updates( $update, $item ) {

This caused error in debug.log:
PHP Notice: Undefined property: stdClass::$plugin in /home4/nataliad/testsite.nataliadrause.com/wp-content/plugins/wp-rocket/inc/classes/subscriber/Plugin/class-updater-subscriber.php on line 272

After the submitted code modification there are no errors in debug.log

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[piotrbak]

@Tabrisrp Can we add any code to simulate this issue?

edit. Sorry, I can see it in the description.

[piotrbak]

Tested scenario mentioned in the description. Auto-updates related to WP Rocket are still disabled (Enable auto-updates not present), related to other plugins are visible. No log entries:
testrail-report-149.pdf

@Tabrisrp Is that enough?

[Tabrisrp]

Yes that's good enough 👍🏼

It's an edge case, and we added an extra guard clause to avoid the PHP notice.