Member variable does not accept array with elements - php

Question

After updating WordPress to 6.0.2, I get the "white screen of death" - just stating that
there is a critical error
with no further explanation.
After some debugging I located the line, that produces the error:
/wp-content/plugins/jet-theme-core/includes/locations.php line 53
It's a function of the class Jet_Theme_Core_Locations that assigns an array to $this->_locations[ $id ]
With these declarations
private $_locations = array();
public $test = array();
private $_test = array();
I tested some statements and found out that
$this->_locations = true; // works
$this->_locations = "test"; // works
$this->_locations = array(); // works
$this->_locations = array("test"); // produces a critical error
$this->_locations = array("test" => "test"); // produces a critical error
$this->_locations[] = "test"; // produces a critical error
$this->_locations["test"] = "test"; // produces a critical error
$test = array("test" => "test"); // works
$this->test = array(); // works
$this->test = array("test"); // works
$this->_test = array(); // works
$this->_test = array("test"); // works
I must be missing something. Probably something really obvious. But I can't figure out, what it is.
[Edit:]
The PHP log file says:
PHP Fatal error: Uncaught Error: Class 'Elementor\\Post_CSS_File' not found in /wp-content/plugins/jet-theme-core/includes/locations.php:106

Answer 1

The function enqueue_styles() loops over $this->_locations and calls Elementor\Post_CSS_File but doesn't find it. If $this->_locations is empty or not an array at all, it doesn't touch Elementor\Post_CSS_File and the error doesn't occur.
As suggested here, I replaced
$css_file = new Elementor\Post_CSS_File( $template_id );
with
$css_file = new Elementor\Core\Files\CSS\Post( $template_id );
Now everything works fine.