Runtime Error '91' Object variable or With Block variable not set.

Hello,

Thanks for helping.

I'm getting a
Runtime Error '91'
Object variable or With Block variable not set.
when I run a button that creates a pie chart from a set of data:

When I hit debug, this is what highlights:
ActiveChart.ChartType = xlPie

Sub Chart_Earnings() 'Pie chart for earnings

Dim Sheetname As String
Sheetname = ActiveSheet.Name

Call DeleteCharts
    Range("J21,A1:A6,C1:C6").Select
    Range("C6").Activate
    Charts.Add
    ActiveChart.ChartType = xlPie
    ActiveChart.SetSourceData Source:=Sheets(Sheetname).Range("A1:A6,C1:C6"), _
        PlotBy:=xlColumns
    ActiveChart.Location Where:=xlLocationAsObject, Name:=Sheetname
    ActiveChart.HasLegend = True
    ActiveChart.Legend.Select
    Selection.Position = xlRight

End Sub

Do you have any idea what is wrong?

Thank you.