stop filling new [] in pie defaults

Author: alexcjohnson

src/traces/pie/calc.js

@@ -18,7 +18,7 @@ module.exports = function calc(gd, trace) {
     var vals = trace.values;
     var hasVals = Array.isArray(vals) && vals.length;
     var labels = trace.labels;
-    var colors = trace.marker.colors;
+    var colors = trace.marker.colors || [];
     var cd = [];
     var fullLayout = gd._fullLayout;
     var colorWay = fullLayout.colorway;

src/traces/pie/defaults.js

@@ -34,8 +34,7 @@ module.exports = function supplyDefaults(traceIn, traceOut, defaultColor, layout
     var lineWidth = coerce('marker.line.width');
     if(lineWidth) coerce('marker.line.color');
 
-    var colors = coerce('marker.colors');
-    if(!Array.isArray(colors)) traceOut.marker.colors = [];
+    coerce('marker.colors');
 
     coerce('scalegroup');
     // TODO: hole needs to be coerced to the same value within a scaleegroup