This happens in in Ardour's Preference dialog with
e.g. BufferingOptions:
~OptionEditorContainer deletes the Option, which in turn
deletes the Widget BufferingOptions:_buffering_presets_combo
Since the widget is not managed it is not removed from its
parent.
Later ~OptionEditorContainer disposes the page layout, which
eventually also calls the Frame d'tor, causing a heap-use-after-free.
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