Exclude admin/config from being disabled to avoid requirements error

Closes #3490248

advagg.module

@@ -3311,6 +3311,7 @@ function advagg_enabled() {
     // Disable advagg if on admin page and configured to do so.
     // AND theme is admin theme
     // AND NOT /admin/reports/status
+    // AND NOT /admin/config
     // AND NOT /admin/config/development/performance/.
     // AND NOT /admin/appearance/settings/*.
     // AND NOT /admin/config/development/performance/advagg/*.
@@ -3318,6 +3319,7 @@ function advagg_enabled() {
       && $GLOBALS['theme'] === $admin_theme
       && path_is_admin($current_path)
       && !($arg[1] === 'reports' && $arg[2] === 'status')
+      && !($arg[1] === 'config' && empty($arg[2]))
       && !($arg[2] === 'development' && $arg[3] === 'performance' && empty($arg[4]))
       && !($arg[1] === 'appearance' && $arg[2] === 'settings' && !empty($arg[3]))
       && stripos($current_path, $config_path . '/advagg') !== 0