Fix php warnings

public/main/gradebook/gradebook_flatview.php

@@ -282,7 +282,7 @@ if (isset($_GET['isStudentView']) && $_GET['isStudentView'] == 'false') {
         $simple_search_form
     );
     $flatViewTable->display();
-} elseif (isset($_GET['selectcat']) && ($_SESSION['studentview'] == 'teacherview')) {
+} elseif (isset($_GET['selectcat']) && isset($_GET['isStudentView']) && ($_SESSION['studentview'] == 'teacherview')) {
     DisplayGradebook::display_header_reduce_flatview(
         $cat[0],
         $showeval,

public/main/gradebook/lib/be/exerciselink.class.php

@@ -38,11 +38,10 @@ class ExerciseLink extends AbstractLink
      */
     public function get_all_links($getOnlyHotPotatoes = false)
     {
-        $tableItemProperty = Database::get_course_table(TABLE_ITEM_PROPERTY);
+        //$tableItemProperty = Database::get_course_table(TABLE_ITEM_PROPERTY);
         $exerciseTable = $this->get_exercise_table();
         $lpItemTable = Database::get_course_table(TABLE_LP_ITEM);
-
-        $documentPath = api_get_path(SYS_COURSE_PATH).$this->course_code.'/document';
+        //$documentPath = api_get_path(SYS_COURSE_PATH).$this->course_code.'/document';
         if (empty($this->course_code)) {
             return [];
         }

public/main/inc/lib/document.lib.php

@@ -4071,8 +4071,7 @@ class DocumentManager
         $comment = null;
         $title = get_lang('Default certificate');
         $fileName = api_replace_dangerous_char($title);
-        $filePath = api_get_path(SYS_COURSE_PATH)."{$courseData['directory']}/document$dir";
-
+        //$filePath = api_get_path(SYS_COURSE_PATH)."{$courseData['directory']}/document$dir";
         /*if (!is_dir($filePath)) {
             mkdir($filePath, api_get_permissions_for_new_directories());
         }*/