Type checking in function _form_validate in form.inc

The patch should also check that the value is a string so as to prevent deprecation notices when NULL is passed to mb_strlen() by drupal_strlen().

I would say that the problem mentioned in the IS can happen only if there is a field with #maxlength attribute, which expects an array (for example the select form element). However according to the Form API documentation, #maxlength is only allowed on these elements: machine_name, password, textfield. I do not think either of them could have a value of array. Therefore this is likely a programming error, which is not something the Drupal 7 core should sanitize.

I am closing this as Works as designed. If someone can provide steps to reproduce which will work on the clean D7 install according to the Form API docs, then feel free to reopen this. Thanks!