GeoJsonViewer example cannot open files.

The GeoJsonViewer cannot open files with the file dialog.

The file dialog returns, e.g.: QUrl("file:///C:/Users/Matti/qt5/qtlocation/examples/location/geojson_viewer/data/10-countries.json")
and url.path() transforms it to: "/C:/Users/Matti/qt5/qtlocation/examples/location/geojson_viewer/data/10-countries.json"
QFile cannot open this path because of the leading "/".

A workaround is to use url.toLocalFile(), but maybe we should make sure fileDialog -> QFile(url.path()) works.