There has been a problem UTF-8 characters in the configuration file since 2006 (!), as the length of the data to be written was mis- calculated. We can omit the specification of the data length at all when just passing a QByteArray object to QFile::write(). Fixes setup dialog appearing each start if one of the configured paths in the setup dialog contains non-ASCII characters. Closes #3348920, #3017409, #2812054.