[MusicXML import] incorrectly swapped title frame due to extra vbox
When importing MusicXML generated by MuseScore from file W04 - Gentle Maiden+Maid of Glenconnel (JMS, 2019-01-08)(1p).mscz, attached to #290533: MusicXML export issues in @BanjoJake's Jan 17, 2021 - 05:34 reply, the titles are incorrectly swapped.
This is caused the algorithm that tries to detect and fix the Sibelius "title at the bottom" style, which does not take systems into account and incorrectly assumes the text "The Maid of Glenconnel" is also part of a bottom title.
See function addCreditWords() in importmxmlpass1.cpp, where const bool doSwap is initialised incorrectly due to the text "The Maid of Glenconnel" being found in the lower half of the page.
Workaround: manually swap the title texts.