minor tweaks to error handling to allow for defaulted values from pre v2.6 data

netbox/utilities/templatetags/helpers.py

@@ -171,6 +171,8 @@ def divide(x, y):
     """
     Return x/y (rounded).
     """
+    if x is None or y is None:
+        return None
     return round(x / y)
 
 
@@ -179,6 +181,8 @@ def percentage(x, y):
     """
     Return x/y as a percentage.
     """
+    if x is None or y is None:
+        return None
     return round(x / y * 100)