Added missing error messages for server config form.

interface/web/admin/lib/lang/en_server_config.lng

@@ -32,4 +32,9 @@ $wb["gateway_txt"] = 'Gateway';
 $wb["hostname_txt"] = 'Hostname';
 $wb["nameservers_txt"] = 'Nameservers';
 $wb["auto_network_configuration_txt"] = 'Network Configuration';
+$wb["ip_address_error_wrong"] = 'Invalid IP address format.';
+$wb["netmask_error_wrong"] = 'Invalid Netmask format.';
+$wb["gateway_error_wrong"] = 'Invalid Gateway format.';
+$wb["hostname_error_empty"] = 'Hostname is empty.';
+$wb["nameservers_error_empty"] = 'Nameserver is empty.';
 ?>
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