Hide all abstract classes from ILS dropdown.

module/VuFind/src/VuFind/Controller/InstallController.php

@@ -555,11 +555,11 @@ class InstallController extends AbstractBase
                 = opendir(APPLICATION_PATH . '/module/VuFind/src/VuFind/ILS/Driver');
             $drivers = [];
             $blacklist = [
-                'Sample.php', 'Demo.php', 'DriverInterface.php', 'AbstractBase.php',
-                'PluginManager.php',
+                'Sample.php', 'Demo.php', 'DriverInterface.php', 'PluginManager.php',
             ];
             while ($line = readdir($dir)) {
                 if (stristr($line, '.php') && !in_array($line, $blacklist)
+                    && substr($line, 0, 8) !== 'Abstract'
                     && substr($line, -11) !== 'Factory.php'
                     && substr($line, -9) !== 'Trait.php'
                 ) {