After installation of cache : no more access to admin.php

[fiammybe]

After installation of #170 , I can no longer access admin.php.
'''
Uncaught exception
Message: Call to a member function getItem() on null
Code: 0
File: C:\xampp71\htdocs\gitalpha7\impresscms\admin.php
Line: 54
Trace:
#0 C:\xampp71\htdocs\gitalpha7\impresscms\htdocs\index.php(114): require()
#1 {main}
'''