in the GUI, that dark synchronise screen, if "Progress increase per hour" goes negative, then "Estimated time left until synced" says "%n left", not integers, but '%n'. I was expecting a meaningful wording, like "unknown" or "infinity".

## can you reproduce the problem?
I get this behavour by suspending a non-synced node for a few hours and then restoring it.

### What version of bitcoin-core are you using?
0.15.99

## machine:
Atom 330, 2GB RAM, 5400 RPM HDD, GNU/Linux
{
    delete ui;
}
bool ModalOverlay::eventFilter(QObject * obj, QEvent * ev) {
    if (obj == parent()) {
        if (ev->type() == QEvent::Resize) {
            QResizeEvent * rev = static_cast<QResizeEvent*>(ev);
            resize(rev->size());
            if (!layerIsVisible)
                setGeometry(0, height(), width(), height());
        }
        else if (ev->type() == QEvent::ChildAdded) {
            raise();
        }
    }
    return QWidget::eventFilter(obj, ev);
}
bool ModalOverlay::event(QEvent* ev) {