J 3.7.5 > 3.8: Class 'JParameter' not found - Joomla! Forum - community, help and support

joomla crashing on update attempts 3.7.5 3.8. i'm not sure whether issue rockettheme template (2 active) or joomla.

trying update joomla 3.7.5 3.8 , getting following errors:

notice: undefined offset: 8 in /home/xxxxxxxx/public_html/libraries/gantry/core/gantry.class.php on line 1302
error displaying error page: call member function update() on null: class 'jparameter' not found

line 1302 below line starting if ($checks_override...

code: select all

// add browser checked files or override
               foreach ($template_check_paths $check_index => $check) {
                  // replace $check override if exists
                  if ($checks_override[$check_index]) {
                     $check = $override_checks[$check_index];
                  }


i notice, when logged site's backend (before upgrade attempt) in extensions/templates, when click on templates on lefthand menu (styles/templates) message:

0 call member function get() on boolean

when turn on debug, see this:

call stack
# function location
1 () jroot/administrator/components/com_templates/views/templates/tmpl/default.php:85
2 include() jroot/libraries/legacy/view/legacy.php:694
3 jviewlegacy->loadtemplate() jroot/libraries/legacy/view/legacy.php:229
4 jviewlegacy->display() jroot/administrator/components/com_templates/views/templates/view.html.php:73
5 templatesviewtemplates->display() jroot/libraries/legacy/controller/legacy.php:671
6 jcontrollerlegacy->display() jroot/administrator/components/com_templates/controller.php:73
7 templatescontroller->display() jroot/libraries/legacy/controller/legacy.php:709
8 jcontrollerlegacy->execute() jroot/administrator/components/com_templates/templates.php:21
9 require_once() jroot/libraries/cms/component/helper.php:389
10 jcomponenthelper::executecomponent() jroot/libraries/cms/component/helper.php:364
11 jcomponenthelper::rendercomponent() jroot/libraries/cms/application/administrator.php:98
12 japplicationadministrator->dispatch() jroot/libraries/cms/application/administrator.php:156
13 japplicationadministrator->doexecute() jroot/libraries/cms/application/cms.php:265
14 japplicationcms->execute() jroot/administrator/index.php:51

i have no idea means, there's wrong install. have attempted locate , remove unused , old extensions, no help. and, cannot find joomla 3.7.5 full package re-install.

gantry framework template. contact template developer update.