Allow a null label for a DataSet
diff --git a/MPChartLib/src/com/github/mikephil/charting/data/DataSet.java b/MPChartLib/src/com/github/mikephil/charting/data/DataSet.java
index ca170fa..c7a7caf 100644
--- a/MPChartLib/src/com/github/mikephil/charting/data/DataSet.java
+++ b/MPChartLib/src/com/github/mikephil/charting/data/DataSet.java
@@ -337,7 +337,7 @@
      */
     public String toSimpleString() {
         StringBuffer buffer = new StringBuffer();
-        buffer.append("DataSet, label: " + mLabel + ", entries: " + mYVals.size() + "\n");
+        buffer.append("DataSet, label: " + (mLabel == null ? "" : mLabel) + ", entries: " + mYVals.size() + "\n");
         return buffer.toString();
     }
 
diff --git a/MPChartLib/src/com/github/mikephil/charting/renderer/LegendRenderer.java b/MPChartLib/src/com/github/mikephil/charting/renderer/LegendRenderer.java
index 1f4f426..6e0578d 100644
--- a/MPChartLib/src/com/github/mikephil/charting/renderer/LegendRenderer.java
+++ b/MPChartLib/src/com/github/mikephil/charting/renderer/LegendRenderer.java
@@ -92,9 +92,11 @@
                     colors.add(clrs.get(j));
                 }
 
-                // add the legend description label
-                colors.add(-2);
-                labels.add(bds.getLabel());
+                if (bds.getLabel() != null) {
+                    // add the legend description label
+                    colors.add(-2);
+                    labels.add(bds.getLabel());
+                }
 
             } else if (dataSet instanceof PieDataSet) {
 
@@ -107,9 +109,11 @@
                     colors.add(clrs.get(j));
                 }
 
-                // add the legend description label
-                colors.add(-2);
-                labels.add(pds.getLabel());
+                if (pds.getLabel() != null) {
+                    // add the legend description label
+                    colors.add(-2);
+                    labels.add(pds.getLabel());
+                }
 
             } else { // all others