Custom fields: creating an option with a quote in the option label causes SQL error

When creating a new custom field, and adding options after the field has been created, civicrm escapes the string twice, causing an SQL error.

How to reproduce:

• create a custom field, type Integer, widget Select
• add an option for the field, save
• go back to the management of the field options, add a new one:
  • Label: L'été
  • Value: 123 (doesn't matter)

Saving will cause an SQL error.

I isolated the code to: civicrm/CRM/Custom/Form/Option.php formRule()

$optionLabel = CRM_Utils_Type::escape($fields['label'], 'String');
$optionValue = CRM_Utils_Type::escape($fields['value'], 'String');

I don't think it is necessary to escape() the strings here, because the DB calls later pass the params as 'string':

$params = array(
1 => array($optionGroupId, 'Integer'),
2 => array($optionLabel, 'String'),
);