Settings form validation error

The field "Synchronous tag loading position" in the Settings form is Required and also hidden if the "Tag loading" is set to "Asynchronous".
This makes it impossible to submit the form as you get validation error for the hidden field.
User must set Tag loading to "Synchronous", select a value in "Synchronous tag loading position", then set back to "Asynchronous".

Added fix to set $form['sync_load_position'][''#default_value''] = 'top'.