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
{
    showHide(layerIsVisible, true);
    if (!layerIsVisible)
        userClosed = true;
}
void ModalOverlay::showHide(bool hide, bool userRequested)
{
    if ( (layerIsVisible && !hide) || (!layerIsVisible && hide) || (!hide && userClosed && !userRequested))
        return;
    if (!isVisible() && !hide)
        setVisible(true);
    setGeometry(0, hide ? 0 : height(), width(), height());
    QPropertyAnimation* animation = new QPropertyAnimation(this, "pos");
    animation->setDuration(300);
    animation->setStartValue(QPoint(0, hide ? 0 : this->height()));
    animation->setEndValue(QPoint(0, hide ? this->height() : 0));
    animation->setEasingCurve(QEasingCurve::OutQuad);
    animation->start(QAbstractAnimation::DeleteWhenStopped);
    layerIsVisible = !hide;
}
void ModalOverlay::closeClicked()
{
    showHide(true);
    userClosed = true;
}