Taxonomy: Prevent `wp_list_categories()` from producing not well-nested output...

Taxonomy: Prevent `wp_list_categories()` from producing not well-nested output if `hide_title_if_empty` is true.

Props chesio.
Fixes #38839. See #33460.
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git-svn-id: https://core.svn.wordpress.org/trunk@39220 1a063a9b-81f0-0310-95a4-ce76da25c4cd