ignore 0-minutes nonstop slots

(nonstop slots are kept in base because tracks link to them)

panikweb/views.py

@@ -282,6 +282,8 @@ class Grid(TemplateView):
 
         nonstops = []
         for nonstop in Nonstop.objects.all():
+            if nonstop.start == nonstop.end:
+                continue
             if nonstop.start < nonstop.end:
                 nonstops.append([nonstop.start.hour + nonstop.start.minute/60.,
                                  nonstop.end.hour + nonstop.end.minute/60.,