Internal helper function used to extract a specified field from a list of records.
If a field value is NULL, it is replaced with an empty string ("").
.safe_extract(x, field)A character vector containing the extracted values, with NULLs replaced by "".
Internal function (not designed to be used directly by end users)
A list of lists (records), coming from parsed JSON API responses.
A character string naming the field to extract from each record.