[SOLVED] MijoAnalytics - Error after installation!

There is an error. Please report the message (Piwik 2.8.3) and full backtrace in the Piwik forums (please do a Search first as it might have been reported already!).

Strict Notice: Only variables should be assigned by reference in /home/isarab2014/public_html/plugins/system/social_presence/social_presence.php on line 41

Backtrace -->

#0 Piwik\Error::errorHandler(…) called at [/home/isarab2014/public_html/plugins/system/social_presence/social_presence.php:41]
#1 plgSystemSocial_presence->onAfterRender(…) called at [:]
#2 call_user_func_array(…) called at [/home/isarab2014/public_html/libraries/joomla/event/event.php:71]
#3 JEvent->update(…) called at [/home/isarab2014/public_html/libraries/joomla/event/dispatcher.php:162]
#4 JEventDispatcher->trigger(…) called at [/home/isarab2014/public_html/libraries/joomla/application/base.php:106]
#5 JApplicationBase->triggerEvent(…) called at [/home/isarab2014/public_html/libraries/cms/application/cms.php:994]
#6 JApplicationCms->render(…) called at [/home/isarab2014/public_html/libraries/cms/application/administrator.php:436]
#7 JApplicationAdministrator->render(…) called at [/home/isarab2014/public_html/libraries/cms/application/cms.php:257]
#8 JApplicationCms->execute(…) called at [/home/isarab2014/public_html/administrator/index.php:42]

It seems to me that the plugin you have installed (social_presence) is an old plugin for Piwik 1.*. The warning is shown because of that plugin, and looking at the error message it seems the plugin might not be compatible with Piwik 2.