tq_get fails to return earnings using alphavantage as the source

[walts]

tq_get fails to return earnings and issues a warning message with the following code run with a valid Alphavantage api key:

library(tidyverse)
library(tidyquant)

av_api_key( YOUR ALPHA VANTAGE API KEY)

earn <- tq_get( c("KBR", "AAPL"), get = "alphavantage", av_fun = "EARNINGS",outputsize = "full")

which returns

Warning message:
There were 4 warnings in dplyr::mutate().
The first warning was:
ℹ In argument: data.. = purrr::map(...).
Caused by warning in stri_c():
! argument is not an atomic vector; coercing