QUrl fromUserInput creates invalid urls

QUrl has a different behavior when using the constructor vs. fromUserInput(). When trying to create a QUrl with the following invalid url :///home/hag/Pictures/below.png the constructor creates an empty QUrl and throws an error "Relative URL's path component contains ':' before any '/'; source was \":///home/hag/Pictures/below.png\"; path = \":///home/hag/Pictures/below.png\"", but the fromUserInput() function accepts the same invalid url without any errors and creates a local version of the url resulting in the following url file::///home/hag/Pictures/below.png.
The following snippet should demonstrate the problem:

QString str = QString(":///home/hag/Pictures/below.png");

QUrl defaultUrl = QUrl(str);
QUrl userUrl = QUrl::fromUserInput(str);

qDebug() << "raw" << str;
qDebug() << "default" << defaultUrl;
qDebug() << "user" << userUrl;

qDebug() << "ERROR default" << defaultUrl.errorString();
qDebug() << "ERROR user" << userUrl.errorString();

Output

raw ":///home/hag/Pictures/below.png"
default QUrl("")
user QUrl("file::///home/hag/Pictures/below.png")
ERROR default "Relative URL's path component contains ':' before any '/'; source was \":///home/hag/Pictures/below.png\"; path = \":///home/hag/Pictures/below.png\""
ERROR user ""

The fromUserInput() function needs a more sophisticated check than

...
// Check first for files, since on Windows drive letters can be interpretted as schemes
if (QDir::isAbsolutePath(trimmedString))
    return QUrl::fromLocalFile(trimmedString);
...

This only checks if the given url is an absolute path which basically checks if it is a relative path and then negates the result. So whenever the provided url in fromUserInput() is not a relative path, this function will return the given url with the additional prefix file:.