Hi again,
I fixed the errors.
1. In the plugin file sm-gallery.php on line 72 remove the 3rd array element with the value ‘1’ from the 2nd parameter of add_action. So it changes from this:
add_action('get_footer', array($this, 'conditional_gallery_script_enqueue', 1));
… to this:
add_action('get_footer', array($this, 'conditional_gallery_script_enqueue'));
2. In the plugin file sm-gallery.php move line 20…
add_action( 'plugins_loaded', array ( 'sm_gallery_plugin', 'get_instance' ) );
… to below the definition of the class sm_gallery_plugin
That fixed all the errors for me. Perhaps a patch and a new version 1.1.19 is in order ??