A semi-opaque ribbon is observed in the main window:

![DeepinScreenshot_bitcoin-qt_20200119212040](https://user-images.githubusercontent.com/32963518/72686984-752bce80-3b02-11ea-8e54-a4d0e6448c1f.png)

![DeepinScreenshot_bitcoin-qt_20200119212253](https://user-images.githubusercontent.com/32963518/72686986-7a891900-3b02-11ea-87b8-cb2a7ff5b791.png)

Tab switching does not remove it. Window moving does not remove it.
It vanishes after window resizing.

**To reproduce**
Run with `-regtest`, generate some blocks (200 in my case), then quit.
Remove `rev00000.dat` file to trigger an error.
Run with `-regtest` and in the dialog "Do you want to rebuild the block database now?" click "OK".

**System information**
Linux Mint 19.3 + Cinnamon 4.4.8

Both versions affected:
- 0.19.0.1 (gitian)
- master + system Qt 5.9.7
#include <qt/modaloverlay.h>
#include <qt/forms/ui_modaloverlay.h>
#include <qt/guiutil.h>
#include <chainparams.h>
#include <QResizeEvent>
#include <QPropertyAnimation>
ModalOverlay::ModalOverlay(bool enable_wallet, QWidget *parent) :
QWidget(parent),
ui(new Ui::ModalOverlay),
bestHeaderHeight(0),
bestHeaderDate(QDateTime()),
layerIsVisible(false),
userClosed(false)
{
    ui->setupUi(this);
    connect(ui->closeButton, &QPushButton::clicked, this, &ModalOverlay::closeClicked);
    if (parent) {
        parent->installEventFilter(this);
        raise();
    }
    blockProcessTime.clear();
    setVisible(false);
    if (!enable_wallet) {
        ui->infoText->setVisible(false);
        ui->infoTextStrong->setText(tr("%1 is currently syncing.  It will download headers and blocks from peers and validate them until reaching the tip of the block chain.").arg(PACKAGE_NAME));
    }
}
ModalOverlay::~ModalOverlay()