Do not set a history amount if we do not have a valid update interval

Rather than setting it to 100, set it to 0 so it is at least very clear
when things are broken.

faces/facepackages/linechart/contents/ui/LineChart.qml

@@ -93,7 +93,7 @@ Charts.LineChart {
             }
 
             interval: sensorsModel.ready ? sensorsModel.headerData(index, Qt.Horizontal, Sensors.SensorDataModel.UpdateInterval) : 0
-            maximumHistory: interval > 0 ? (chart.historyAmount * 1000) / interval : 100
+            maximumHistory: interval > 0 ? (chart.historyAmount * 1000) / interval : 0
             fillMode: Charts.HistoryProxySource.FillFromEnd
         }
         onObjectAdded: {