add test for next <n> stepping over lines with no returns

Author: WillHalto

test/console/control_flow_commands_test.rb

@@ -21,7 +21,9 @@ def program
         10|
         11| s = Student.new("John")
         12| s.name
-        13| "foo"
+        13| puts "foo"
+        14| puts "bar"
+        15| "baz"
       RUBY
     end
 
@@ -84,6 +86,8 @@ def test_next_with_number_goes_to_the_next_nth_line
         assert_line_num 11
         type 'n 2'
         assert_line_num 13
+        type 'n 2'
+        assert_line_num 15
         type 'quit'
         type 'y'
       end