PyQt translates python integers to signed 32 bits int when emitting a int in a signal.
We need to specifically emit a 64 bit integer. See https://doc.qt.io/qt-5/qtglobal.html#quint64-typedef
Also apply the same fix to the two signals that I previously fixed in a different way (with a larger performance overhead) in https://github.com/Bitcoin-ABC/ElectrumABC/pull/291