从wordpress woothemes插件中删除（条件）动作

i simply want to remove a message block by using functions.php. This is the action i wish to remove:

    if( empty( $active_ids ) ){    
                    add_action( 'sensei_loop_course_inside_before', 
                    array( $this, 'active_no_course_message_output' ) );        
    }

so i figure i had to refer to the class before i could access it's function i wish to remove, so i did:

function remove_no_active_courses_message(){
    //classname where the function i want to remove is:
    //class Sensei_Shortcode_User_Courses implements Sensei_Shortcode_Interface 

    remove_action( 'sensei_loop_course_inside_before', array( 'Sensei_Shortcode_User_Courses', 'active_no_course_message_output' ) ); 
    remove_action( 'sensei_loop_course_inside_before', array( $Sensei_Shortcode_User_Courses, 'active_no_course_message_output' ) ); 

}
add_action('sensei_loop_course_inside_before', 'remove_no_active_courses_message'); 

But neither of the 2 worked, any suggestions?

Edit: source class: https://github.com/Automattic/sensei/blob/master/includes/shortcodes/class-sensei-shortcode-user-courses.php

Edit 2 (note: when i try to global the class object, it var dumps null on this class so maybe the problem is i cant access it's global element? the woothemes sensei object works fine and i can print stuff from that. but not accessing the function via the class object instance) I tried some of the suggested answers:

    function remove_no_active_courses_message(){
        //classname where the function i want to remove is:
        //class Sensei_Shortcode_User_Courses implements Sensei_Shortcode_Interface 

        global $Sensei_Shortcode_User_Courses; //DOESNT SEEM TO INSTANTIATE?
        global $woothemes_sensei; //WORKS FINE AND CAN ACCES IT'S OBJECTS HERE

        //var_dump($Sensei_Shortcode_User_Courses); //PRINTS NULL
        //var_dump($woothemes_sensei); //PRINTS THE ENTIRE THINGY SUCCESFULLY

        remove_action( 'sensei_loop_course_inside_before', array( $Sensei_Shortcode_User_Courses, 'active_no_course_message_output' ), 99 );

}   
    add_action('wp_footer', 'remove_no_active_courses_message');    

Just asking, its there a way that this files is called after functions.php?

This is ugly but let´s tried,

1. Create a function that return and empty string:

      function emptyString(){
         return ' ';
      }
   

2. Then add to the hook

    add_action('sensei_loop_course_inside_before', 'emptyString', 11)
   

Let's do this and check if something happens