title: Rendering CombinedChartView using Swift Charts
body: <p>I am using <a href="https://github.com/danielgindi/Charts" rel="nofollow noreferrer">https://github.com/danielgindi/Charts</a> and able to successfully render LineChartView.  However, trying to render a very simple CombinedChartView renders as a blank chart.  Also, any touch event will output "CGAffineTransformInvert: singular matrix."</p>
  
  <pre><code>@IBOutlet weak var chartView: CombinedChartView!
  
  var lineData = [ChartDataEntry]()
  lineData.append(ChartDataEntry(x: Double(0), y: drand48()))
  let lineDataSet = LineChartDataSet(values: lineData, label: "line")
  
  var barData = [BarChartDataEntry]()
  barData.append(BarChartDataEntry(x: Double(0), y: drand48()))
  let barDataSet = BarChartDataSet(values: barData, label: "bar")
  
  let combinedData = CombinedChartData(dataSets: [lineDataSet, barDataSet])
  chartView.data = combinedData
  charView.notifyDataSetChanged()
  </code></pre>
  
  <p>Am I totally missing something here?
  Thank you.</p>