Use weakref for tabs in QShortCut lambdas
Use weakref for tabs in QShortCut lambdas

Unfortunately we have no way to directly destroy or remove the
lambdas embedded in the QShortcut objects, so this is the
only solution to avoid leaking references.  As the QShortcut
objects have the window as parent, they are destroyed with the
window so dangling refs to the destroyed window can't happen.

This and 91349d109e8c6d32578f64519de09f9c3e00d28c fix #1549.

molecular/electrum,dashpay/electrum-dash,digitalbitbox/electrum,argentumproject/electrum-arg,neocogent/electrum,asfin/electrum,wakiyamap/electrum-mona,pooler/electrum-ltc,imrehg/electrum,pooler/electrum-ltc,dashpay/electrum-dash,romanz/electrum,FairCoinTeam/electrum-fair,cryptapus/electrum-uno,vertcoin/electrum-vtc,digitalbitbox/electrum,cryptapus/electrum-uno,dabura667/electrum,fireduck64/electrum,vialectrum/vialectrum,argentumproject/electrum-arg,imrehg/electrum,procrasti/electrum,FairCoinTeam/electrum-fair,FairCoinTeam/electrum-fair,cryptapus/electrum-myr,fujicoin/electrum-fjc,pknight007/electrum-vtc,neocogent/electrum,dashpay/electrum-dash,pooler/electrum-ltc,fyookball/electrum,spesmilo/electrum,fyookball/electrum,kyuupichan/electrum,asfin/electrum,aasiutin/electrum,cryptapus/electrum,romanz/electrum,molecular/electrum,procrasti/electrum,pknight007/electrum-vtc,kyuupichan/electrum,lbryio/lbryum,protonn/Electrum-Cash,cryptapus/electrum-uno,cryptapus/electrum-uno,pooler/electrum-ltc,aasiutin/electrum,wakiyamap/electrum-mona,fujicoin/electrum-fjc,vertcoin/electrum-vtc,romanz/electrum,procrasti/electrum,argentumproject/electrum-arg,spesmilo/electrum,digitalbitbox/electrum,vertcoin/electrum-vtc,vialectrum/vialectrum,fireduck64/electrum,protonn/Electrum-Cash,molecular/electrum,fyookball/electrum,neocogent/electrum,digitalbitbox/electrum,fireduck64/electrum,aasiutin/electrum,dabura667/electrum,asfin/electrum,vertcoin/electrum-vtc,lbryio/lbryum,kyuupichan/electrum,spesmilo/electrum,procrasti/electrum,imrehg/electrum,dabura667/electrum,aasiutin/electrum,molecular/electrum,fireduck64/electrum,cryptapus/electrum-myr,pknight007/electrum-vtc,FairCoinTeam/electrum-fair,spesmilo/electrum,fujicoin/electrum-fjc,vialectrum/vialectrum,protonn/Electrum-Cash,cryptapus/electrum,wakiyamap/electrum-mona,pknight007/electrum-vtc,wakiyamap/electrum-mona,argentumproject/electrum-arg,cryptapus/electrum-myr,cryptapus/electrum,dabura667/electrum,imrehg/electrum,protonn/Electrum-Cash,cryptapus/electrum-myr,dashpay/electrum-dash