The issue is the ole "division by zero" when trying to compute percentages. How kind of PHP to treat this as a warning and not fatal error! However it might clutter the logs or cause unexpected behaviour for some users, so it should be fixed.
Make sure to test when they have:
- Zero live edits but non-zero deleted edits
- Zero deleted edits but non-zero live edits
- Zero edits total
I think it is still useful to show the EditCounter even if they have zero edits total, because there could be stats on logged actions, global edits and account age.
Example: http://xtools-dev.wmflabs.org/ec/en.wikipedia.org/Niharika (warnings suppressed in production)