Prevent NPE

Author: hannesa2

MPChartLib/src/main/java/com/github/mikephil/charting/charts/PieChart.java

@@ -809,12 +809,13 @@ public String getAccessibilityDescription() {
 
         PieData pieData = getData();
 
-        int entryCount = pieData.getEntryCount();
+		int entryCount = 0;
+		if (pieData != null)
+			entryCount = pieData.getEntryCount();
 
         StringBuilder builder = new StringBuilder();
 
-        builder.append(String.format(Locale.getDefault(), "The pie chart has %d entries.",
-                entryCount));
+        builder.append(String.format(Locale.getDefault(), "The pie chart has %d entries.", entryCount));
 
         for (int i = 0; i < entryCount; i++) {
             PieEntry entry = pieData.getDataSet().getEntryForIndex(i);

MPChartLib/src/main/java/com/github/mikephil/charting/interfaces/dataprovider/ChartInterface.java

@@ -6,6 +6,8 @@
 import com.github.mikephil.charting.formatter.IValueFormatter;
 import com.github.mikephil.charting.utils.MPPointF;
 
+import androidx.annotation.Nullable;
+
 /**
  * Interface that provides everything there is to know about the dimensions,
  * bounds, and range of the chart.
@@ -63,6 +65,7 @@ public interface ChartInterface {
 
     IValueFormatter getDefaultValueFormatter();
 
+    @Nullable
     ChartData getData();
 
     int getMaxVisibleCount();