The hosting support also wrote me this:
I am not familiar with indexhibit but here is the error log:
root@/home/…# tail logs/ninafrankova.ninja/http/error.log
[Sun Jul 23 09:55:07 2017] [error] [client 90.177.28.176] malformed
header from script. Bad header=Not Found: index.php
[Sun Jul 23 09:55:07 2017] [error] [client 90.177.28.176] File does not
exist: /home/ninfra2/ninafrankova.ninja/internal_error.html
[Sun Jul 23 09:55:18 2017] [error] [client 90.177.28.176] malformed
header from script. Bad header=Not Found: index.php
[Sun Jul 23 09:55:18 2017] [error] [client 90.177.28.176] File does not
exist: /home/ninfra2/ninafrankova.ninja/internal_error.html
[Sun Jul 23 10:30:45 2017] [error] [client 172.248.140.91] malformed
header from script. Bad header=Not Found: index.php
[Sun Jul 23 10:30:45 2017] [error] [client 172.248.140.91] File does not
exist: /home/ninfra2/ninafrankova.ninja/internal_error.html
[Sun Jul 23 10:39:49 2017] [error] [client 172.248.140.91] malformed
header from script. Bad header=Not Found: index.php
[Sun Jul 23 10:39:49 2017] [error] [client 172.248.140.91] File does not
exist: /home/ninfra2/ninafrankova.ninja/internal_error.html
[Sun Jul 23 10:41:25 2017] [error] [client 172.248.140.91] malformed
header from script. Bad header=Not Found: index.php
[Sun Jul 23 10:41:25 2017] [error] [client 172.248.140.91] File does not
exist: /home/ninfra2/ninafrankova.ninja/internal_error.html