Potential typo in statistics.go

I spotted a potential error on line 258 of statistics.go

```
var parentRatingKey int = 0
parentRatingKeyInt, err := strconv.Atoi(fmt.Sprintf("%v", tautulli_data[j].ParentRatingKey))
if err == nil {
	grandparentRatingKey = parentRatingKeyInt
}
```

Shouldn't this be assigning to parentRatingKey instead?