stacked graph attempt / 3

noblogsmv/webapp.py

@@ -31,8 +31,12 @@ _palette = ['ffa07a',
 
 
 def _mk_stacked_graph(chart, valuelist):
-    n = len(valuelist[0])
+    if valuelist:
+        n = len(valuelist[0])
+    else:
+        n = 1
     v0 = [0] * n
+    chart.add_data(v0)
     for j, values in enumerate(valuelist):
         for i, v in enumerate(values):
             if v: