Fix division by 0

Author: hannesa2

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

@@ -791,12 +791,14 @@ protected void drawMarkers(Canvas canvas) {
 			}
 
 			// callbacks to update the content
-			int markerIndex = i % mMarkers.size();
-            IMarker markerItem = mMarkers.get(markerIndex);
-            markerItem.refreshContent(e, highlight);
+			if (!mMarkers.isEmpty()) {
+				int markerIndex = i % mMarkers.size();
+				IMarker markerItem = mMarkers.get(markerIndex);
+				markerItem.refreshContent(e, highlight);
 
-			// draw the marker
-			markerItem.draw(canvas, pos[0], pos[1]);
+				// draw the marker
+				markerItem.draw(canvas, pos[0], pos[1]);
+			}
 		}
 	}