Fix flow when no grids

c3.js

@@ -4020,7 +4020,7 @@
                 // update x domain to generate axis elements for flow
                 updateXDomain(targetsToShow, true, true);
                 // update elements related to x scale
-                flushXGrid(true);
+                if (flushXGrid) { flushXGrid(true); }
 
                 // generate transform to flow
                 translateX = (x(flowStart.x) - x(flowEnd.x)) * (isTimeSeries ? 0.9 : 1); // TODO: fix 0.9, I don't know why 0.9..

htdocs/samples/api_flow_timeseries.html

@@ -65,7 +65,7 @@
 //            ['data2', 100, 100],
             ['data3', 200, 150],
           ],
-          min: new Date('2013-01-20'),
+          to: new Date('2013-01-20'),
         });
       }, 1000);