gui/kivy: fix installwizard back button behaviour
gui/kivy: fix installwizard back button behaviour

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