Fatal error: Call to a member function update() on null

Question

I'm installing a plugin on an Learning Management System called Ilias. It's installed correctly, but when I'm trying to update it to make it active it gives this fatal error:

"Fatal error: Call to a member function update() on null in C:\xampp\htdocs\ilias\Services\Component\classes\class.ilObjComponentSettingsGUI.php on line 520"

Which refers of this piece of code:

function updatePlugin()
{
    include_once("./Services/Component/classes/class.ilPlugin.php");
    $pl = ilPlugin::getPluginObject($_GET["ctype"], $_GET["cname"],
        $_GET["slot_id"], $_GET["pname"]);

    $result = $pl->update();

    if ($result !== true)
    {
        ilUtil::sendFailure($pl->message, true);
    }
    else
    {
        ilUtil::sendSuccess($pl->message, true);
    }

The mentioned line is this one:

$result = $pl->update();

And this is the 'included' file code:

    <?php

    abstract class ilPluginConfigGUI

{
    protected $plugin_object = null;

    /**
     * Set plugin object
     *
     * @param   object  plugin object
     */
    final function setPluginObject($a_val)
    {
        $this->plugin_object = $a_val;
    }

    /**
     * Get plugin object
     *
     * @return ilPlugin  object
     */
    public final function getPluginObject()
    {
        return $this->plugin_object;
    }

    /**
     * Execute command
     *
     * @param
     * @return
     */
    function executeCommand()
    {
        global $ilCtrl, $ilTabs, $lng, $tpl;

        $ilCtrl->setParameterByClass("ilobjcomponentsettingsgui", "ctype", $_GET["ctype"]);
        $ilCtrl->setParameterByClass("ilobjcomponentsettingsgui", "cname", $_GET["cname"]);
        $ilCtrl->setParameterByClass("ilobjcomponentsettingsgui", "slot_id", $_GET["slot_id"]);
        $ilCtrl->setParameterByClass("ilobjcomponentsettingsgui", "plugin_id", $_GET["plugin_id"]);
        $ilCtrl->setParameterByClass("ilobjcomponentsettingsgui", "pname", $_GET["pname"]);

        $tpl->setTitle($lng->txt("cmps_plugin").": ".$_GET["pname"]);
        $tpl->setDescription("");

        $ilTabs->clearTargets();

        if($_GET["plugin_id"])
        {
            $ilTabs->setBackTarget(
                $lng->txt("cmps_plugin"),
                $ilCtrl->getLinkTargetByClass("ilobjcomponentsettingsgui", "showPlugin")
            );
        }
        else
        {
            $ilTabs->setBackTarget(
                $lng->txt("cmps_plugins"),
                $ilCtrl->getLinkTargetByClass("ilobjcomponentsettingsgui", "listPlugins")
            );
        }

        $this->performCommand($ilCtrl->getCmd("configure"));

    }

    abstract function performCommand($cmd);
}
?>

I don' t understand the error as I didn't change any of the code and all these files were included in the plugin. I hope someone can point out my mistake, thank you!

UPDATE

protected function beforeUpdate()
{
    return true;    // false would indicate that anything went wrong
    // update would not proceed
    // throw an exception in this case
    //throw new ilPluginException($lng->txt(""));
}

/**
 * After update processing
 */
protected function afterUpdate()
{
}

/**
 * Get plugin object.
 *
 * @param   string  $a_ctype    IL_COMP_MODULE | IL_COMP_SERVICE
 * @param   string  $a_cname    component name
 * @param   string  $a_sname    plugin slot name
 * @param   string  $a_pname    plugin name
 */
final static function getPluginObject($a_ctype, $a_cname, $a_slot_id, $a_pname)
{
    global $ilDB;

    include_once("./Services/Component/classes/class.ilPluginSlot.php");
    $slot_name = ilPluginSlot::lookupSlotName($a_ctype, $a_cname, $a_slot_id);

    $cached_component = ilCachedComponentData::getInstance();
    $rec = $cached_component->lookCompId($a_ctype, $a_cname);
    if (! $rec) {
        return NULL;
    } 

Answer 1

Your problem is indicated by the following item in your output (see comments):

$_GET["pname"] --> string(26) "SystemNotifications-master"

Probably by checking out from the GIT-Repo you created a folder named "SystemNotifications-master". This does not match the naming convention that the plugin folder must have in ILIAS, which would probably be in this case: "SystemNotifications". It must match parts of the php plugin class (which probably is something like ilSystemNotificationsPlugin).

In any case, do not change the core code of ILIAS. The problem is surely not there, but in your file system/database.