[Bug]: Grand child doesn't have subject counts

### What happened?

```r
data <- teal_data()
data <- within(data, {
parent <- data.frame(id = 1:10, a = runif(10), b = runif(10))
child <- data.frame(id = 1:100, parent_id = rep(1:10, each = 10), c = runif(100), d = runif(100))
grand_child <- data.frame(id = 1:1000, child_id = rep(1:100, each = 10), e = runif(1000), f = runif(1000))
})
join_keys(data) <- join_keys(
join_key("child", "parent", keys = c("parent_id" = "id")),
join_key("grand_child", "child", keys = c("child_id" = "id"))
)

app <- init(
data = data,
modules = example_module()
)
shinyApp(app$ui, app$server)

```