fix divide by zero when no HPC slice exists
diff --git a/planetstack/core/plus/views.py b/planetstack/core/plus/views.py
index 705f4f6..3c63e16 100644
--- a/planetstack/core/plus/views.py
+++ b/planetstack/core/plus/views.py
@@ -517,6 +517,8 @@
 class DashboardSummaryAjaxView(View):
     def get(self, request, **kwargs):
         def avg(x):
+            if len(x)==0:
+                return 0
             return float(sum(x))/len(x)
 
         sites = getCDNOperatorData().values()