Avoids needing to iterate and append the characters in one case. This also
alters the function to not need to construct a temporary std::string
(QString's toUtf8() is sufficient, as QByteArray exposes iterators).
toStdString() is equivalent to retrieving the QString's underlying
QByteArray via calling QString's .toUtf8 member function and then
calling .toStdString() on the result of it (discarding the QByteArray
afterwords), so this just trims off an unnecessary step in the process.
This is also somewhat more indicative of the conversions going on:
toStdString() converts the underlying character sequence of a
QString to UTF-8, not strict ASCII, so we're really using a superset of
ASCII.