Update date.lib.php

If $duration_unit = 's', it shows a 500 error

htdocs/core/lib/date.lib.php

@@ -121,7 +121,9 @@ function getServerTimeZoneInt($refgmtdate = 'now')
 function dol_time_plus_duree($time, $duration_value, $duration_unit, $ruleforendofmonth = 0)
 {
 	global $conf;
-
+	if ($duration_unit == 's') {
+	    return $time + ($duration_value);
+	}
 	if ($duration_value == 0) {
 		return $time;
 	}