Missing $conf in function initialize_session of app.inc.php
I found an issue in app.inc.php, which results in unavailable $conf variable. The function initialize_session uses $this->_conf and $conf, but $conf is not available in function, because of missing global statement. We do need this, because to override Template before being logged in (multi tenancy).
I see 2 ways to fix this. Either to use global $conf statement at the beginning of function, or rewrite $conf via $this->_conf. Best way should be to use "global $conf", like in log function for example.
I will create an merge request, decide by yourself, which way you would like to go :)