When generating full-path CSS/XPath selectors, elements with id
attributes had their selector appended twice — once in the id branch
(line 30) and again unconditionally (line 50).
This produced selectors like 'body > #main > #main > #target > #target'
instead of the correct 'body > #main > #target'.
Move the append into the else branch so it only fires for elements
without an id (elements with id already append in the if branch).
Includes 2 regression tests.