PHP Warning: Undefined array key when rollback any theme

[Mai-Saad]

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• Made sure you’re on the latest version => 3.12.5.3
• Used the search feature to ensure that the bug hasn’t been reported before

Describe the bug
When rollback any theme while WPR is enabled, we will get the following warning
[15-Feb-2023 09:08:58 UTC] PHP Warning: Undefined array key "themes" in /var/www/new.rocketlabsqa.ovh/htdocs/wp-content/plugins/wp-rocket/inc/common/purge.php on line 563

To Reproduce
Steps to reproduce the behavior:
1. Rollback plugin is enabled
2. WPR is enabled
3. Try to rollback any theme
4. Check debug.log

Expected behavior
No warning when rollback

Additional context
Add any other context about the problem here.

• tested on Nginx/Apache
• same warning exists with 3.11.5

Backlog Grooming (for WP Media dev team use only)

• Reproduce the problem
• Identify the root cause
• Scope a solution
• Estimate the effort

[mostafa-hisham]

Reproduce the problem ✔️

Identify the root cause

$hook_extra array can not hold a theme key

Scope a solution

We need to check if the hook array contains 'theme' key

	if ( ! isset ($hook_extra['themes']) || ! is_array( $hook_extra['themes'] ) ) {
		return;
	}

Estimate the effort

Effort XS