FIX : Compatibility v21

manualreconciliation.php

@@ -699,7 +699,7 @@ elseif ($reshook == 0) {
 					setEventMessages($langs->trans("ErrorFieldRequired", $langs->transnoentitiesnoconv("DateDue")), null, 'errors');
 					$error++;
 				}
-				if (empty($social_contribution->period)) {
+				if (isset($social_contribution->period) && empty($social_contribution->period) || isset($social_contribution->periode) && empty($social_contribution->periode)) {
 					$langs->load('errors');
 					setEventMessages($langs->trans("ErrorFieldRequired", $langs->transnoentitiesnoconv("Period")), null, 'errors');
 					$error++;