Recently closed issue showing up as `NA`

Running this as of 2022-02-03, I get `NA` for last issue closed in dplyr repo when it should be 0 days (7 hours ago).
```
> library(packagemetrics)
> library(dplyr)
> 
> dplyr_and_dt <- package_list_metrics(c("dplyr", "data.table"))
> glimpse(dplyr_and_dt)
Rows: 2
Columns: 17
$ package            <chr> "dplyr", "data.table"
...
$ last_issue_closed  <dbl> NA, 0
```