Fix condition for last available unit

courses/models.py

@@ -214,6 +214,9 @@ class Course(models.Model):
                 lessons.append(lesson)
         return lessons
 
+    def last_public_lesson(self):
+        return published
+
     def first_lesson(self):
         if self.lessons.exists():
             return self.lessons.all()[0]
@@ -506,6 +509,8 @@ class CourseStudent(models.Model):
                                                     status='published').order_by('position')
                     if next_units:
                         next_unit = next_units.first()
+                    elif cur_lesson == self.course.public_lessons[-1]:
+                        next_unit = last_unit_done.unit
 
             if next_unit:
                 return next_unit