Profile value reset on submit.

Hello Team! I've noticed that if user hasn't permission to edit a field the value of this field will be reset on submit. For example administrator add something to this field. However normal user without permission to edit this field go to edit form and save it. This will reset protected field value.
This is caused by unset($form[$category][$key]) function because the field is not visible but profile module will insert empty value for this field. A possible solution of this is:

//unset($form[$category][$key]);
$form[$category][$key]['#type'] = 'value';
$form[$category][$key]['#value'] = isset($form[$category][$key]['#default_value']) ? $form[$category][$key]['#default_value'] : '';