Stud.IP: PluginManager Plugin construction loop fix

PluginManager.class.php

<?php
class PluginManager
{
    // ...
    
    /**
     * Get instance of the plugin specified by plugin meta data.
     *
     * @param Array $plugin_info   plugin meta data
     * @param mixed $context       context range id (optional and deprecated)
     * @throws Exception when running into a plugin's constructor loop
     */
    protected function getCachedPlugin ($plugin_info, $context = NULL)
    {
        $class = $plugin_info['class'];
        $path  = $plugin_info['path'];

        if (isset($this->plugin_cache[$class])) {
            return $this->plugin_cache[$class];
        }

        if (array_key_exists($class, $this->plugin_cache) && $this->plugin_cache[$class] === null) {
            throw new Exception("Plugin constructor loop detected. Avoid refering to the same plugin through PluginEngine in the plugin's constructor");
        }

        $this->plugin_cache[$class] = null;

        $plugin_class = $this->loadPlugin($class, $path);

        if ($plugin_class) {
            $plugin = $plugin_class->newInstance();
        }

        return $this->plugin_cache[$class] = $plugin;
    }

    // ...
}