[ci skip] Fix #5590 (add a default error message for FV valid_base64 rule)
diff --git a/system/language/english/form_validation_lang.php b/system/language/english/form_validation_lang.php
index 305de37..842c1ae 100644
--- a/system/language/english/form_validation_lang.php
+++ b/system/language/english/form_validation_lang.php
@@ -43,6 +43,7 @@
$lang['form_validation_valid_emails'] = 'The {field} field must contain all valid email addresses.';
$lang['form_validation_valid_url'] = 'The {field} field must contain a valid URL.';
$lang['form_validation_valid_ip'] = 'The {field} field must contain a valid IP.';
+$lang['form_validation_valid_base64'] = 'The {field} field must contain a valid Base64 string.';
$lang['form_validation_min_length'] = 'The {field} field must be at least {param} characters in length.';
$lang['form_validation_max_length'] = 'The {field} field cannot exceed {param} characters in length.';
$lang['form_validation_exact_length'] = 'The {field} field must be exactly {param} characters in length.';