dolibarr-develop, php 7.2.7

On third party, add bank account. After spanish account has been added, on summary screen
..../htdocs/societe/paymentmodes.php

a correct account number causes the error:
Warning: A non-numeric value encountered in .......\public_html\dolibarr-develop\htdocs\core\lib\bank.lib.php on line 359

This is
`$sum += $values[$i] * substr($InumCta, $i, 1);`

Since substr returns a string it cannot be summed (I assume).

I changed it to
`$sum += $values[$i] * (int)substr($InumCta, $i, 1)`

htdocs/core/lib/bank.lib.php

@@ -356,7 +356,7 @@ function checkES($IentOfi, $InumCta)
     $sum = 0;
 
     for ($i = 0; $i < 11; $i++) {
-        $sum += $values[$i] * substr($InumCta, $i, 1);
+        $sum += $values[$i] * (int)substr($InumCta, $i, 1);//int to cast result of substr to a number
     }
 
     $key = 11 - $sum % 11;