Merge pull request #1875 from michaelarnauts/master

Ignore null values when calculating scale

src/Chart.Core.js

@@ -409,8 +409,13 @@
 				maxSteps = Math.floor(drawingSize/(textSize * 1.5)),
 				skipFitting = (minSteps >= maxSteps);
 
-			var maxValue = max(valuesArray),
-				minValue = min(valuesArray);
+			// Filter out null values since these would min() to zero
+			var values = [];
+			each(valuesArray, function( v ){
+				v == null || values.push( v );
+			});
+			var minValue = min(values),
+			    maxValue = max(values);
 
 			// We need some degree of separation here to calculate the scales if all the values are the same
 			// Adding/minusing 0.5 will give us a range of 1.