MDL-82663 user: fix check for current user removing own enrolment.

We only need to remove the current user from selection if they were
ever part of the selection originally.

user/action_redir.php

@@ -231,7 +231,7 @@ if ($formaction == 'bulkchange.php') {
         $filteredusers = array_filter($users, $matchesplugin);
 
         // If the bulk operation is deleting enrolments, we exclude in any case the current user as it was probably a mistake.
-        if ($operationname === 'deleteselectedusers' && (!in_array($USER->id, $removed))) {
+        if ($operationname === 'deleteselectedusers' && array_key_exists($USER->id, $filteredusers)) {
             \core\notification::warning(get_string('userremovedfromselectiona', 'enrol', fullname($USER)));
             unset($filteredusers[$USER->id]);
         }

user/tests/behat/bulk_editenrolment.feature

@@ -53,8 +53,10 @@ Feature: Bulk enrolments
     When I log in as "teacher1"
     And I am on "Course 1" course homepage
     And I navigate to course participants
+    # Select all three users (the teacher themselves and both students).
     And I click on "Select all" "checkbox"
     And I set the field "With selected users..." to "Delete selected user enrolments"
+    # Teacher is informed that they've been removed from current selection.
     Then I should see "User \"Teacher 1\" was removed from the selection."
     And the following should exist in the "generaltable" table:
       | Name      | Status |
@@ -63,7 +65,6 @@ Feature: Bulk enrolments
     And I should not see "Teacher 1" in the "generaltable" "table"
     And I press "Unenrol users"
     And I should see "2 unenrolled users"
-    And I should see "User \"Teacher 1\" was removed from the selection."
     And I should see "Teacher 1" in the "participants" "table"
     And I should not see "Student 1" in the "participants" "table"
     And I should not see "Student 2" in the "participants" "table"