Top Performing course issue fix

Author: sanjana4khan

classes/Instructor.php

@@ -778,7 +778,7 @@ public static function get_top_performing_courses_by_instructor( $instructor_id,
 					COALESCE(earnings.total_revenue, 0)  AS total_revenue,
 					COALESCE(enrollments.total_student, 0) AS total_student
 				FROM wp_posts post
-				LEFT JOIN ({$earnings_sql}) earnings 
+				INNER JOIN ({$earnings_sql}) earnings 
 					ON earnings.course_id = post.ID
 				LEFT JOIN ({$enrollment_sql}) enrollments 
 					ON enrollments.course_id = post.ID