Fix for not refreshing labels after changing to NONE

[pktiuk]

Closes: #436

[pktiuk]

Adding additional call of method JoyButton::buildActiveZoneSummaryString after clearSlotsEventReset fixes issue, but it is very not elegant solution.

void JoyButtonContextMenu::clearButton()
{
    QMetaObject::invokeMethod(button, "clearSlotsEventReset");
    QMetaObject::invokeMethod(button, "buildActiveZoneSummaryString");
}

It would be much better to just add calling buildActiveZoneSummaryString inside clearSlotsEventReset, but it causes app to freeze. (Blocking on mutex)

    if (numActiveSlots > 0)
    {
        tempLock = &activeZoneLock;
        iter = &activeSlotsIter;
    } else
    {
        tempLock = &assignmentsLock; //This one
        iter = &assignmentsIter;
    }

    QReadLocker tempLocker(tempLock);