QKeySequence and detecting invalid input

There should be some way of detecting invalid input given to QKeySequence(const QString &str)

With this app the output is: QKeySequence("K")
This makes it hard to allow users to type in their own shortcuts.

#include <QKeySequence>
#include <QDebug>
int main()
{
QKeySequence seq("XYZ+K");
qDebug() << seq;
return 0;
}