Issue translating free y scales

Works

``` r
p <- ggplot(txhousing, aes(month, median)) + 
  geom_line(aes(group = city)) + geom_smooth(method = "gam") + 
  facet_wrap(~ year)
ggplotly(p)
```

missing traces

``` r
p <- ggplot(txhousing, aes(month, median)) + 
  geom_line(aes(group = city)) + geom_smooth(method = "gam") + 
  facet_wrap(~ year, scales = "free_y")
ggplotly(p)
```
