QDir::homePath() does not work as documented on non-Windows OS

Checking QString home.isNull() is never true if HOME environment variable is not set, it's empty (""). Should use isEmpty() instead.

QString QFileSystemEngine::homePath()
{
QString home = QFile::decodeName(qgetenv("HOME"));
if (home.isNull())
home = rootPath();
return QDir::cleanPath(home);
}