Call to undefined method Piwik\Updater::addComponentToCheck() (no replies)

Hello !

I'm posting here because after an automatic update from 2.10.0 to 2.12 I am now having the following error :

Fatal error: Call to undefined method Piwik\Updater::addComponentToCheck() in /homepages/16/d410276458/htdocs/piwik/plugins/CoreUpdater/CoreUpdater.php on line 131

Fatal error: Uncaught exception 'Zend_Session_Exception' with message 'Session must be started before any output has been sent to the browser; output started in /homepages/16/d410276458/htdocs/piwik/plugins/CoreUpdater/CoreUpdater.php/131' in /homepages/16/d410276458/htdocs/piwik/libs/Zend/Session.php:443 Stack trace: #0 /homepages/16/d410276458/htdocs/piwik/libs/Zend/Session/Namespace.php(143): Zend_Session::start(true) #1 /homepages/16/d410276458/htdocs/piwik/core/Session/SessionNamespace.php(34): Zend_Session_Namespace->__construct('CorePluginsAdmi...', false) #2 /homepages/16/d410276458/htdocs/piwik/core/Nonce.php(39): Piwik\Session\SessionNamespace->__construct('CorePluginsAdmi...') #3 /homepages/16/d410276458/htdocs/piwik/plugins/CorePluginsAdmin/Controller.php(364): Piwik\Nonce::getNonce('CorePluginsAdmi...') #4 [internal function]: Piwik\Plugins\CorePluginsAdmin\Controller->safemode(Array) #5 /homepages/16/d410276458/htdocs/piwik/core/FrontController.php(530): call_user_func_array(Array, Array) #6 /homepages/16/d4 in /homepages/16/d410276458/htdocs/piwik/libs/Zend/Session.php on line 443

I have found these 2 similar errors :
- [forum.piwik.org]
- [forum.piwik.org]

In those posts the solution is to manually update Piwik, so obviously that's what I did via SSH commands :

# go into the the directory that contains your existing "piwik/" installation 
$ wget http://builds.piwik.org/piwik.zip # download latest version
$ unzip -o piwik.zip # extract it to "piwik/" directory
$ rm piwik.zip # delete the archive and read below the next step

But it doesn't work at all and the same error message appears :/
I also tried to put back the 2.10.0 piwik files in my folder and the problem still is the same.
In my database the piwik version is 2.10.0

I hope you could help me find a solution as I would prefer not lose all my data and make a clean install :-)

Best regards,
Yann