Adding items to ArrayCollection HELP!

[maasss18]

I'm having trouble adding my items to Array Collection called newDataProviderAC. And newDataProviderAC has to be the ArrayCollection for the lineChart called myChart.
The function addData is running with a timer, so every 0.5secs the line will interpolate and form the next point depending on the HSlider.
The data for the corresponding Renderer is stored in the TestVarItemRenderer in _varRendererCollection
The linechart is hardcoded with id="myChart"
When i run the program it's gives me an error

Main Thread (Suspended: TypeError: Error #1009: Cannot access a property or method of a null object reference.)
Components::TestArea/addData
flash.utils::Timer/_timerDispatch [no source]
flash.utils::Timer/tick [no source]

Here are my codes


[Bindable]
public var ItemVar:TestVarItemRenderer;
[Bindable]
public var newDataProviderAC:ArrayCollection;
[Bindable]
public var newSeriesArray:Array;
[Bindable]
public var newSeries:LineSeries;




private function addData(e:Event):void
{
myChart.dataProvider=newDataProviderAC;
myChart.series= newSeriesArray;
legend.dataProvider=myChart;
for each(var variableItem:TestVarItemRenderer in _varRendererCollection)
{

newSeries = new LineSeries();
trace("creates newSeries");

newSeries.yField=""+variableItem._data.varName;
trace("adds variable name to new series yField");

newSeries.displayName=""+variableItem._data.varName;
trace("adds display name");

newDataProviderAC.addItem({(variableItem._data.var Name):variableItem.HS.value});
trace("adds item to newDPAC")

newSeriesArray.push(newSeries);

}


}