`get_vpts` fails with a 404 for missing data

[bart1]

See aloftdata/data-repository#111 for a description of the missing data

This causes an issue in get_vpts to fail with a rather uninformative error:

require(getRad)
require(dplyr)
get_vpts("deisn", as.Date("2025-7-1")+27:30)
#> Error in `get_vpts()`:
#> ℹ In index: 1.
#> Caused by error in `httr2::req_perform_parallel()`:
#> ! HTTP 404 Not Found.
get_vpts_coverage("baltrad")|> filter(radar=="deisn", date %in%(as.Date("2025-7-1")+27:30))
#> # A tibble: 4 × 5
#>   source  radar date       directory                     file_count
#>   <chr>   <chr> <date>     <chr>                              <dbl>
#> 1 baltrad deisn 2025-07-28 baltrad/hdf5/deisn/2025/07/28        288
#> 2 baltrad deisn 2025-07-29 baltrad/hdf5/deisn/2025/07/29        288
#> 3 baltrad deisn 2025-07-30 baltrad/hdf5/deisn/2025/07/30        288
#> 4 baltrad deisn 2025-07-31 baltrad/hdf5/deisn/2025/07/31        288

It would be good to fail a bit more graceful, maybe throw a warning (something like 404 but data should be there according to coverage) and return anyway?