(unbound) get_interface_subnet(v6) can return null, ignore network in that case.

Eventually we should move this kind of "get all attached networks" to a single and simple function, which uses legacy_get_interface_addresses() underneath. but there's still too much obscure code in this region to remove it easily

src/etc/inc/unbound.inc

@@ -707,15 +707,19 @@ function unbound_acls_config() {
         if (!empty($ifip)) {
             $subnet_bits = get_interface_subnet($ubif);
             $subnet_ip = gen_subnet($ifip, $subnet_bits);
+            if (!empty($subnet_bits) && !empty($subnet_ip)) {
                 $aclcfg .= "access-control: {$subnet_ip}/{$subnet_bits} allow\n";
             }
+        }
         $ifip = get_interface_ipv6($ubif);
         if (!empty($ifip)) {
             $subnet_bits = get_interface_subnetv6($ubif);
             $subnet_ip = gen_subnetv6($ifip, $subnet_bits);
+            if (!empty($subnet_bits) && !empty($subnet_ip)) {
                 $aclcfg .= "access-control: {$subnet_ip}/{$subnet_bits} allow\n";
             }
         }
+    }
 
     // Configure the custom ACLs
     if (isset($config['unbound']['acls'])) {

src/www/services_unbound_acls.php

@@ -348,15 +348,19 @@ include("head.inc");
                       if (!empty($ifip)) {
                           $subnet_bits = get_interface_subnet($ubif);
                           $subnet_ip = gen_subnet($ifip, $subnet_bits);
+                          if (!empty($subnet_bits) && !empty($subnet_ip)) {
                               $automatic_allowed[] = "{$subnet_ip}/{$subnet_bits}";
                           }
+                      }
                       $ifip = get_interface_ipv6($ubif);
                       if (!empty($ifip)) {
                           $subnet_bits = get_interface_subnetv6($ubif);
                           $subnet_ip = gen_subnetv6($ifip, $subnet_bits);
+                          if (!empty($subnet_bits) && !empty($subnet_ip)) {
                               $automatic_allowed[] = "{$subnet_ip}/{$subnet_bits}";
                           }
                       }
+                  }
                   foreach ($automatic_allowed as $network):?>
                   <tr>
                     <td><?=gettext("Internal");?></td>