Upgrade from version 5.0.1 to 5.0.4 or 5.0.3

Hello,
I installed the projeqtor version on local wamp server on my PC and it worked well.
I began to use it and add project and users.
So i tried to upgrade the Projeqtor version to 5.0.4. I unziped the version in the wamp server directory projeqtor.
Since them, when i start the wamp server on the page http://localhost/projeqtor/view/main.php the result is:

Fatal error: Call to a member function save() on a non-object in C:\Users\Public\programmes public\wamp\www\projeqtor\model\AuditSummary.php on line 114
I tried to unzip th V5.0.3 version and i have the same result.
I tried to come back to the V5.0.1 version and it do not work anymore.
Could you help me please?