Update mouvement.php

sometime $year not filled then made "bug" the search
propose to fill with current year in this case

htdocs/product/stock/mouvement.php

@@ -537,8 +537,8 @@ if ($resql)
     		$productidselected=$key;
     		$productlabelselected=$val;
     	}
-		$datebefore=dol_get_first_day($year, $month?$month:1, true);
-		$dateafter=dol_get_last_day($year, $month?$month:12, true);
+		$datebefore=dol_get_first_day($year?$year:strftime("%Y",time()), $month?$month:1, true);
+		$dateafter=dol_get_last_day($year?$year:strftime("%Y",time()), $month?$month:12, true);
     	$balancebefore=$movement->calculateBalanceForProductBefore($productidselected, $datebefore);
     	$balanceafter=$movement->calculateBalanceForProductBefore($productidselected, $dateafter);