Hello,
about a week ago, after  the nightly batch linux updates/upgrades, my site quite working. I removed ALL the plugin subdirectories I had, and the site came back. I've been adding the plugins back one-by-one until i was able to reproduce the error. This is what happens the moment I reinstall the "Manage Properties Photos" plugin:

( ! ) Fatal error: Uncaught Error: Call to a member function fetch_assoc() on boolean in /var/www/piwigo/include/dblayer/functions_mysqli.inc.php on line 220
( ! ) Error: Call to a member function fetch_assoc() on boolean in /var/www/piwigo/include/dblayer/functions_mysqli.inc.php on line 220
Call Stack
#    Time    Memory    Function    Location
1    0.0001    362968    {main}( )    .../admin.php:0
2    0.0001    363808    include_once( '/var/www/piwigo/include/common.inc.php' )    .../admin.php:16
3    0.0614    802368    load_plugins( )    .../common.inc.php:142
4    0.0755    1045960    load_plugin( )    .../functions_plugins.inc.php:430
5    0.0798    1046480    include_once( '/var/www/piwigo/plugins/manage_properties_photos/main.inc.php' )    .../functions_plugins.inc.php:350
6    0.0811    1051688    pwg_db_fetch_assoc( )    .../main.inc.php:61

Piwigo 2.10.2
Operating system: Linux
PHP: 7.0.33-0+deb9u8
MySQL: 5.5.5-10.1.44-MariaDB-0+deb9u1
Graphics Library: ImageMagick 6.9.7-4
Piwigo URL: http://fristersoft.net