[Qt-interest] assert error in qmap "item_exists()"

[Matthias Pospiech]

The assert error happens in qmap.h in this line:
Q_DECLARE_ASSOCIATIVE_ITERATOR(Map)

The QMap I am using contains 3 values which I can insert with no problem 
or error.
However if I try to access the value (last line) I get this assertion:

    QMapIterator<PiezoStage, int> i(stageToChannelMap);
    while (i.hasNext()) {
        if (i.value() == currentChannel) {...


The map is filled using:

    piezoController->mapStageToChannel(PiezoJenaController::X, 0);
    piezoController->mapStageToChannel(PiezoJenaController::Y, 1);
    piezoController->mapStageToChannel(PiezoJenaController::Z, 2);

with:

void PiezoJenaController::mapStageToChannel(PiezoStage stage, int channel)
{
    if (stageToChannelMap.contains(stage)) {
        stageToChannelMap[stage] = channel;
    } else {
        stageToChannelMap.insert(stage, channel);
    }   
}


What am I possibly doing wrong?
Matthias