bug fix: SeriesMarker.NONE causing NPE

xchart-demo/src/main/java/com/xeiam/xchart/demo/charts/date/DateChart01.java

@@ -25,13 +25,18 @@ import java.util.Random;
 
 import com.xeiam.xchart.Chart;
 import com.xeiam.xchart.ChartBuilder;
+import com.xeiam.xchart.Series;
 import com.xeiam.xchart.SwingWrapper;
 import com.xeiam.xchart.demo.charts.ExampleChart;
+import com.xeiam.xchart.style.SeriesMarker;
 
 /**
  * Millisecond Scale
- * 
- * @author timmolter
+ * <p>
+ * Demonstrates the following:
+ * <ul>
+ * <li>Millisecond Scale
+ * <li>Series with no Markers
  */
 public class DateChart01 implements ExampleChart {
 
@@ -68,7 +73,8 @@ public class DateChart01 implements ExampleChart {
       yData.add(Math.random() * i);
     }
 
-    chart.addDateSeries("blah", xData, yData);
+    Series series = chart.addDateSeries("blah", xData, yData);
+    series.setMarker(SeriesMarker.NONE);
 
     return chart;
 

xchart/src/main/java/com/xeiam/xchart/internal/chartpart/PlotContentLineChart.java

@@ -153,8 +153,10 @@ public class PlotContentLineChart extends PlotContent {
         previousY = yOffset;
 
         // paint marker
-        g.setColor(series.getMarkerColor());
-        series.getMarker().paint(g, xOffset, yOffset);
+        if (series.getMarker() != null) {
+          g.setColor(series.getMarkerColor());
+          series.getMarker().paint(g, xOffset, yOffset);
+        }
 
         // paint errorbar
         if (errorBars != null) {