Moving CI website to another server - only blank page showing

Tha domain has changed.
The /application/logs/ folder is empty, only an index.html is there... I don't know, why?

Have you checked $config['log_threshold'] in your config.php?
or the log_path and is the log_folder able to be written to?
is environment set to development?

Thanks! The log_threshold was set to 0, I set it to 4. And I gave write permission to the log folder.
I got this log, when I try to load the page:

ERROR - 2018-07-02 12:21:10 --> Severity: Notice  --> Only variable references should be returned by reference /var/www/html/szig/ci/core/Common.php 257
DEBUG - 2018-07-02 12:21:10 --> Config Class Initialized
DEBUG - 2018-07-02 12:21:10 --> Hooks Class Initialized
DEBUG - 2018-07-02 12:21:10 --> Utf8 Class Initialized
DEBUG - 2018-07-02 12:21:10 --> UTF-8 Support Enabled
DEBUG - 2018-07-02 12:21:10 --> URI Class Initialized
DEBUG - 2018-07-02 12:21:10 --> Router Class Initialized
DEBUG - 2018-07-02 12:21:10 --> No URI present. Default controller set.
DEBUG - 2018-07-02 12:21:10 --> Output Class Initialized
DEBUG - 2018-07-02 12:21:10 --> Security Class Initialized
DEBUG - 2018-07-02 12:21:10 --> Input Class Initialized
DEBUG - 2018-07-02 12:21:10 --> Global POST and COOKIE data sanitized
DEBUG - 2018-07-02 12:21:10 --> Language Class Initialized
DEBUG - 2018-07-02 12:21:10 --> Loader Class Initialized
DEBUG - 2018-07-02 12:21:10 --> Config file loaded: /var/www/html/szig/application/config/SZIG_ver.php
DEBUG - 2018-07-02 12:21:10 --> Helper loaded: url_helper
DEBUG - 2018-07-02 12:21:10 --> Helper loaded: szig_helper
DEBUG - 2018-07-02 12:21:10 --> Database Driver Class Initialized