Rails return to calling function inside if else block

I am using a recursive function.

def abc
   get_course_to_be_deleted( courses, array_course_name, nil )
end

def self.get_course_to_be_deleted( courses, array_course_name, course )
   if array_course_name.blank?
    #### array_course_name = []
   course
  else
     #### array_course_name = ['Science', 'Maths']
     array_course_name.each do |course_name|
     course = courses.detect{ |course| course.name == course_name  }
     course_names = array_course_name - [ course_name ]
     get_course_to_be_deleted( course.children, course_names, course )
  end
 end

end

When array_course_name is blank, course is not getting returned, instead it goes to else block...any solutions???