qt init: shutdown properly if last open window was a wizard
qt init: shutdown properly if last open window was a wizard

fixes #7171

pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum,spesmilo/electrum,pooler/electrum-ltc,wakiyamap/electrum-mona,pooler/electrum-ltc,wakiyamap/electrum-mona,pooler/electrum-ltc,spesmilo/electrum,wakiyamap/electrum-mona,wakiyamap/electrum-mona