MDL-53994 block_feedback: Add missing include

Also, a little scenario has been added to have the behavior
covered and prevent this to happen again.

blocks/feedback/block_feedback.php

@@ -22,6 +22,10 @@
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
+defined('MOODLE_INTERNAL') || die();
+
+require_once($CFG->dirroot . '/mod/feedback/lib.php');
+
 class block_feedback extends block_list {
 
     function init() {

mod/feedback/tests/behat/coursemapping.feature

@@ -222,3 +222,17 @@ Feature: Mapping courses in a feedback
     And I should see "2 (66.67 %)" in the "option e" "table_row"
     And I should see "0" in the "option f" "table_row"
     And I log out
+
+  Scenario: Site feedback deletion hides feedback block completely
+    When I log in as "manager"
+    And I am on site homepage
+    And I follow "Turn editing on"
+    And I add the "Feedback" block
+    And I click on "Delete" "link" in the "//div[contains(@class,'block_site_main_menu')]//li[contains(.,'Course feedback')]" "xpath_element"
+    And I press "Yes"
+    And I follow "Turn editing off"
+    And I am on site homepage
+    Then "Feedback" "block" should not exist
+    And I follow "Course 1"
+    And "Feedback" "block" should not exist
+    And I log out