thermostat: show a dot instead of a zero

soft/thermostat/src/zoneitem.cpp

@@ -47,7 +47,7 @@ void ZoneItem::refresh(void)
 {
 	QString text;
 
-	if (m_temperature_value == FORCE_OFF)
+	if ((m_temperature_value == FORCE_OFF) || !m_available)
 		text += QString("-");
 	else
 		text += QString::number(m_temperature_value);
@@ -64,7 +64,7 @@ void ZoneItem::refresh(void)
 
 	m_temperatureBtn.setText(text);
 
-	if (m_hygro_value == FORCE_OFF)
+	if ((m_hygro_value == FORCE_OFF) || !m_available)
 		text = QString("-");
 	else
 		text = QString::number(m_hygro_value);