Fix for session add/update when studentscanmark is empty but automark set to close

add_form.php

@@ -327,7 +327,7 @@ class mod_attendance_add_form extends moodleform {
             $this->_form->setConstant('previoussessiondate', $data['sessiondate']);
         }
 
-        if ($data['automark'] == ATTENDANCE_AUTOMARK_CLOSE) {
+        if (!empty($data['studentscanmark']) && $data['automark'] == ATTENDANCE_AUTOMARK_CLOSE) {
             $cm            = $this->_customdata['cm'];
             // Check that the selected statusset has a status to use when unmarked.
             $sql = 'SELECT id

update_form.php

@@ -204,7 +204,7 @@ class mod_attendance_update_form extends moodleform {
             $errors['sestime'] = get_string('invalidsessionendtime', 'attendance');
         }
 
-        if ($data['automark'] == ATTENDANCE_AUTOMARK_CLOSE) {
+        if (!empty($data['studentscanmark']) && $data['automark'] == ATTENDANCE_AUTOMARK_CLOSE) {
             $cm            = $this->_customdata['cm'];
             // Check that the selected statusset has a status to use when unmarked.
             $sql = 'SELECT id