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Hi, I am installing locally for testing and the installer is returning:

Install GNU social
Page notice
Initializing...
Starting installation...
Checking database...

Warning: count(): Parameter must be an array or an object that implements Countable in /var/www/html/gnusocial/extlib/DB.php on line 775
Creating database tables...
Database error: DB Error: unknown error

I am using a Ubuntu 18.04 docker container with Apache 2.4, PHP 7.2 and MySQL 5.7. This are my last lines from Apache error log:

[Fri Aug 24 05:20:15.300645 2018] [php7:notice] [pid 21] [client 172.17.0.1:47666] PHP Notice:  Undefined property: WebInstaller::$fileDir in /var/www/html/gnusocial/lib/installer.php on line 138, referer: http://localhost/gnusocial/install.php
[Fri Aug 24 05:20:15.301360 2018] [php7:warn] [pid 21] [client 172.17.0.1:47666] PHP Warning:  count(): Parameter must be an array or an object that implements Countable in /var/www/html/gnusocial/extlib/DB.php on line 775, referer: http://localhost/gnusocial/install.php
[Fri Aug 24 05:20:27.469783 2018] [php7:notice] [pid 15] [client 172.17.0.1:47680] PHP Notice:  Undefined property: WebInstaller::$avatarDir in /var/www/html/gnusocial/lib/installer.php on line 138, referer: http://localhost/gnusocial/
[Fri Aug 24 05:20:27.469813 2018] [php7:notice] [pid 15] [client 172.17.0.1:47680] PHP Notice:  Undefined property: WebInstaller::$fileDir in /var/www/html/gnusocial/lib/installer.php on line 138, referer: http://localhost/gnusocial/
[Fri Aug 24 05:22:56.059062 2018] [php7:notice] [pid 12] [client 172.17.0.1:47702] PHP Notice:  Undefined property: WebInstaller::$avatarDir in /var/www/html/gnusocial/lib/installer.php on line 138, referer: http://localhost/gnusocial/install.php
[Fri Aug 24 05:22:56.059093 2018] [php7:notice] [pid 12] [client 172.17.0.1:47702] PHP Notice:  Undefined property: WebInstaller::$fileDir in /var/www/html/gnusocial/lib/installer.php on line 138, referer: http://localhost/gnusocial/install.php
[Fri Aug 24 05:22:56.059703 2018] [php7:warn] [pid 12] [client 172.17.0.1:47702] PHP Warning:  count(): Parameter must be an array or an object that implements Countable in /var/www/html/gnusocial/extlib/DB.php on line 775, referer: http://localhost/gnusocial/install.php