Regard isMultiple = true when data.xs is specified even if it has only one element - #522 #526

c3.js

@@ -1436,7 +1436,7 @@
     };
     c3_chart_internal_fn.isMultipleX = function () {
         var $$ = this, config = $$.config;
-        return notEmpty(config.data_xs) && $$.hasMultipleX(config.data_xs);
+        return notEmpty(config.data_xs);
     };
     c3_chart_internal_fn.addName = function (data) {
         var $$ = this, name;

src/data.js

@@ -48,7 +48,7 @@ c3_chart_internal_fn.hasMultipleX = function (xs) {
 };
 c3_chart_internal_fn.isMultipleX = function () {
     var $$ = this, config = $$.config;
-    return notEmpty(config.data_xs) && $$.hasMultipleX(config.data_xs);
+    return notEmpty(config.data_xs);
 };
 c3_chart_internal_fn.addName = function (data) {
     var $$ = this, name;