wrong check in QModbusDataUnit::setValue()

Hi all,

  I think there is a bug in  QModbusDataUnit::setValue(qsizetype index, quint16 newValue)...

We should not check the size of the list of values, but check m_valueCount before assigning the newValue

inline void setValue(qsizetype index, quint16 newValue)
    {
        if (m_values.isEmpty() || index >= m_values.size())
            return;
        m_values[index] = newValue;
    }

and initialize (resize) the list of values in the:

 inline void setValueCount(qsizetype newCount) { m_valueCount = newCount;  }

by adding m_values.resize(newCount);

         Giampaolo