PVS-Studio warning V519 for QT

static String variantToSetting(const QVariant& qvariant)
{
    String retVal;

    switch (qvariant.type()) {
    case QVariant::Bool:
        retVal = qvariant.toBool() ? "true" : "false";
    case QVariant::String:
        retVal = qvariant.toString();
    default:
        break;
    }

    return retVal;
}

The break operator is missing.

This suspicious code was found in QT project by PVS-Studio static code analyzer.
Warning message is:
V519 The 'retVal' variable is assigned values twice successively. Perhaps this is a mistake. Check lines: 169, 171. QtWebKit inspectorclientqt.cpp 171

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/