Remove buttons have same property #name.

Hi,
I have a content type with entity reference fields (Unlimited). The remove button have same value of property '#name' for every one of the field's elements ('_und_0_remove_button'). The problem is that into function multiple_fields_remove_button_field_widget_form_alter the field name was getting directly from the element but the field properties are wrapped under a 'target_id' index.